Biotechnology

Lipase An enzyme (one of a class of enzymes)
that catalyzes the hydrolytic cleavage of
lipid molecules (triglycerides) to yield free
fatty acids. Lipase was the first enzyme to
be produced via genetic engineering and
marketed. Lipase also occurs naturally in
cow’s milk, and in the intestines of many
animals (where it aids/assists digestion of
fats that the animal consumes). See also
ENZYME
,
HYDROLYTIC CLEAVAGE
,
TRIGLYCER-
IDES
,
FATS
,
FATTY ACID
,
FREE FATTY ACIDS
,
DIGESTION
 (
WITHIN ORGANISMS
).
Lipid Bilayer A membrane (i.e., thin sheet-
type) structure composed of relatively small
© 2002 by CRC Press LLC

L
lipid molecules which possess both a hydro-
philic (“water loving”) and a hydrophobic
(“water hating”) moiety. These (membrane)
lipids thus spontaneously form closed bimo-
lecular sheets in aqueous (water-containing)
media, in which the hydrophobic ends of
each lipid molecule are in the center of the
bimolecular membrane and the hydrophilic
ends of the lipid molecules are on the outside
(i.e., touching the water molecules). See also
LIPIDS
,
PLASMA MEMBRANE
,
MOIETY
.
Lipid Vesicles See
LIPOSOMES
.
Lipids From the Greek word lipos, fat, lipids
are water-insoluble (fat) biomolecules that are
highly soluble in organic solvents such as
chloroform. Lipids serve as fuel molecules,
highly concentrated energy stores, “signal-
ing” molecules, and components of cell mem-
branes. Membrane lipids are relatively small
molecules that have both a hydrophilic
(“water loving”) and a hydrophobic (“water
hating”) moiety. These (membrane) lipids
spontaneously form closed bimolecular
sheets in aqueous media (water) which are
barriers to the free movement (flow) of polar
molecules. See also 
FATS
,
MOIETY
,
LIPOPROTEIN
,
CHOLESTEROL
,
SIGNALING
,
SIGNALING MOLECULE
,
SIGNAL TRANSDUCTION
,
PLASMA MEMBRANE
,
ANTIOXIDANTS
,
OXIDATIVE STRESS
,
LIPID BILAYER
,
LEUKOTRIENES
,
OLEOSOMES
.
Lipolytic Enzymes See
LIPASE
.
Lipophilic A “fat loving” molecule, or portion
of a molecule. Relating to, or having strong
affinity for, fats or other lipids. See also 
LIPIDS
,
FATS
.
Lipopolysaccharide (LPS) See
ENDOTOXIN
.
Lipoprotein A conjugated protein containing
a lipid or a group of lipids. For example,
low-density lipoproteins (also known as
“bad” cholesterol) are a “package” of cho-
lesterol (lipid) surrounded by a hydrophilic
protein. Low-density lipoproteins (LDLPs)
and very low-density lipoproteins (VLDLs)
are the specific lipoproteins that are most
likely to deposit cholesterol (plaque) on
artery walls, which increases risk of coro-
nary heart disease (CHD). See also 
PROTEIN
,
LOW
-
DENSITY LIPOPROTEINS
  (
LDLP
),
VERY LOW
-
DENSITY LIPOPROTEINS
  (
VLDL
),
CONJUGATED
PROTEIN
,
HYDROPHILIC
,
LIPIDS
,
CHOLESTEROL
,
APOLIPOPROTEINS
.
Lipoprotein-Associated Coagulation (Clot)
Inhibitor (LACI) A protein that prevents
formation of blood clots. This occurs
because LACI inhibits the controlled series
of zymogen activations (enzymatic cascade)
which causes the formation of fibrinogen
(precursor to fibrin), leading subsequently to
clot formation. See also 
FIBRIN
,
FIBRONECTIN
,
ZYMOGENS
.
Liposomes Also called lipid vesicles or vesi-
cle. Aqueous (watery) compartments
enclosed by a lipid bilayer. They can be
formed by suspending a suitable lipid, such
as phosphatidyl choline, in an aqueous
medium. This mixture is then sonicated (i.e.,
agitated by high- frequency sound waves) to
give a dispersion of closed vesicles (i.e.,
compartments) that are quite uniform in size.
Alternatively, liposomes can be prepared by
rapidly mixing a solution of lipid in ethanol
with water, which yields vesicles that are
nearly spherical in shape and have a diame-
ter of 500 Å (Angstroms). Larger vesicles
(10,000 Å or 1 mm, or 0.00003937 inch in
diameter) can be prepared by slowly evapo-
rating the organic solvent from a suspension
of phospholipid in a mixed solvent system.
Liposomes can be made to contain certain
drugs for protective, controlled release deliv-
ery to targeted tissues. For example, phar-
maceuticals which tend to be rapidly
degraded in the bloodstream could be
enclosed within liposomes so that more of
the nondegraded pharmaceutical would
remain by the time it reached the targeted
tissue. The controlled release property
enables larger doses (of drugs possessing
toxic side effects) to be prescribed, knowing
that the drug will be released in the body
over an extended period of time. See also
LIPIDS
,
MICRON
,
ANGSTROM
 (
Å
).
Lipoxidase See
LIPOXYGENASE
 (
LOX
).
Lipoxygenase (LOX) A “family” of enzymes
that is naturally produced within its seeds
(soybeans) by the soybean plant (Glycine
max (L.) Merrill). In the presence of mois-
ture and certain other conditions, lipoxyge-
nase enzymes catalyze a chemical reaction
in which objectionable “beany” flavor can
be produced from certain components of the
soybean. That “beany” flavor decreases the
© 2002 by CRC Press LLC

L
suitability of resultant soybean raw materials
for manufacture of human foods in some
countries.
Prevention of the reactions that create the
“beany” flavor can be accomplished via heat
denaturation (of lipoxygenases present in the
soybeans) or via creation of soybeans that
do not contain any lipoxygenase enzymes
(known as “LOX null” soybeans). Lipoxy-
genase enzymes also catalyze a reaction in
which certain volatile chemicals are pro-
duced that inhibit growth of any Aspergillus
flavus fungus. See also 
ENZYME
,
SOYBEAN
PLANT
,
LOX NULL SOYBEANS
,
LOX
-
1
,
LOX
-
2
,
LOX-
3
.
Lipoxygenase Null See
LOX NULL SOYBEANS
,
LIPOXYGENASE
 (
LOX
).
Listeria monocytogenes Refers to the “fam-
ily” (numerous strains) of Listeria monocy-
togenes bacteria, that can grow in many
different foodstuffs (e.g., meats) under spe-
cific conditions, and can cause food poison-
ing (Listeriosis) in humans who subsequently
consume those foodstuffs. When consumed
by humans, certain strains/serotypes of List-
eria monocytogenes can cause fever, severe
headaches, stiffness, nausea, diarrhea, and
possibly miscarriages in pregnant women.
As of January 19, 2001, all meat processed
in the U.S. is required to be tested for the
presence of Listeria monocytogenes. See
also
BACTERIA
,
STRAIN
,
SEROTYPES
,
ENTERO-
TOXIN
,
BACTERIOCINS
,
CADHERINS
.
Living Modified Organism (LMO) See
GMO
.
LMO (Living modified organism) See
GMO
.
Loci The plural of locus. See also 
LOCUS
.
Locus The position of a gene on a chromo-
some. See also 
GENE
,
CHROMOSOMES
.
Loop A single-stranded region at the end of a
hairpin in RNA (or single-stranded DNA). It
corresponds to the sequence between
inverted repeats in duplex DNA. See also
RIBONUCLEIC ACID
  (
RNA
),
DEOXYRIBONUCLEIC
ACID
 (
DNA
),
SEQUENCE
 (
OF A DNA MOLECULE
).
LOSBM Low-oligosaccharide soybean meal.
See also 
LOW
-
STACHYOSE SOYBEANS
,
SOYBEAN
PLANT
.
Low-Density Lipoproteins (LDLP) So-called
“bad” cholesterol (i.e., LDL cholesterol),
which carries cholesterol molecules from the
digestive system (e.g., intestine) to body
cells and can sometimes clog arteries over
time (a disease called atherosclerosis, or cor-
onary heart disease). Since cholesterol does
not dissolve in water (which constitutes most
of the volume of blood), the body makes
LDL cholesterol (derived from the digestion
of fatty foods) into little “packages” sur-
rounded by a hydrophilic (“water loving”)
protein. That protein “wrapper” is known as
apolipoprotein B-100, or apo B-100, and it
enables LDL cholesterol to be transported in
the bloodstream because the apolipoprotein
B-100 is attracted to water molecules in the
blood. Part of the apolipoprotein B-100 mol-
ecule also will bind to special LDLP receptor
molecules in the liver, which then clears
those (bound) cholesterol packages out of
the body as part of regular liver functions.
See also 
HIGH
-
DENSITY LIPOPROTEINS
  (
HDLP
s
),
HYDROPHILIC
,
RECEPTORS
,
PROTEIN
,
SITOSTANOL
,
ISOFLAVONES
,
WATER SOLUBLE FIBER
,
CHOLES-
TEROL
,
CORONARY HEART DISEASE
  (
CHD
),
APO-
LIPOPROTEINS
,
VERY LOW
-
DENSITY LIPOPROTEINS
(
VLDL
).
Low-Linolenic Oil Soybeans Soybeans from
soybean (Glycine max) plant varieties which
have been bred specifically to produce soy-
beans bearing oil that contains less than 4%
linolenic acid, instead of the typical 8% lino-
lenic acid content of soybean oil produced
from traditional varieties of soybeans. Low-
linolenic soybean oil would tend to have
greater flavor stability (especially at elevated
temperatures utilized in frying foods) than
soybean oil from traditional varieties of soy-
beans. See also 
SOYBEAN PLANT
,
SOYBEAN OIL
,
FATTY ACID
,
LINOLENIC ACID
,
POLYUNSATURATED
FATTY ACIDS
 (
PUFA
).
Low-lipoxygenase Soybeans See
L O X
-
N U L L
SOYBEANS
.
Low-Phytate Corn Developed in the U.S.
during the 1990s, these are corn (maize)
hybrids possessing the Lpa1 gene, the Lpa2
gene, or the HAP (highly available phospho-
rous) gene (which was discovered by Victor
Raboy). That gene causes corn (maize)
hybrids possessing it to produce much less
phytate than the 0.15% typically present in
traditional varieties of corn (maize).
Because phytate is not digestible in
humans and other monogastric animals
© 2002 by CRC Press LLC

L
(swine, poultry, etc.), substituting low-
phytate corn in place of traditional corn vari-
eties in those animals’ diets helps lessen
adverse environmental impact of animal
feeding (e.g., phosphorous emissions in
excess of annual cropland requirements).
Swine fed a diet in which traditional corn
(maize) varieties have been replaced by low-
phytate corn (maize) produce up to 30% less
phosphorous in their manure, thereby less-
ening the phosphorous impact of those swine
on the environment. Humans consuming a
diet based heavily on corn/maize (e.g., tor-
tillas) absorb 50% more iron when tradi-
tional corn varieties are replaced by low-
phytate corn varieties. That is because the
phytate (inositol hexaphosphate) molecule
“binds”/chelates iron (and some other met-
als) within the digestive system and prevents
their absorption into the body. See also 
CORN
,
PHYTATE
,
HIGH
-
PHYTASE CORN
,
PHYTASE
,
VALUE
-
ENHANCED GRAINS
,
HIGHLY
-
AVAILABLE
PHOSPHOROUS
 (
HAP
)
GENE
,
CHELATION
,
CHELAT-
ING AGENT
,
IRON DEFICIENCY ANEMIA
 (
IDA
).
Low-Phytate Soybeans Developed in the
U.S. during the 1990s, these are soybean
varieties possessing less than 0.30% (of total
soybean weight) phytate, vs. the typical
0.45% phytate content of soybeans from tra-
ditional soybean varieties.
Because phytate is not digestible in
humans and other monogastric animals
(swine poultry, etc.), substituting low-
phytate soybeans in place of traditional soy-
bean varieties in those animals’ diets helps
to lessen adverse environmental impact of
animal feeding (e.g., manure phosphorous
emissions in excess of cropland require-
ments). Swine fed a diet in which traditional
soybean varieties have been replaced by low-
phytate soybeans produce up to 20% less
phosphorous in their manure, thereby less-
ening the phosphorous impact of those swine
on the environment. Due to the fact that the
amino acids lysine, methionine, cysteine,
arginine, and threonine all become more
“bioavailable” (i.e., available for the animal
to build its body tissue, or otherwise utilize)
in a low-phytate diet, low-phytate diets also
help reduce exess nitrogen emissions. See
also
SOYBEAN PLANT
,
PHYTATE
,
LOW
-
PHYTATE
CORN
,
HIGH
-
PHYTASE CORN
/
SOYBEANS
,
LYSINE
,
CYSTEINE
,
METHIONINE
,
ARGININE
,
THREONINE
,
DEAMINATION
.
Low-Stachyose Soybeans T h o s e   s o y b e a n
varieties that contain lower than 1% levels
of the relatively indigestible stachyose car-
bohydrate (and thus higher levels of easily
digestible other nutrients) than traditional
varieties of soybeans (which typically con-
tain 1.4–4.1% stachyose in traditional soy-
bean varieties). Compared to traditional
varieties of soybeans, low-stachyose soy-
beans have approximately 10% more metab-
olizable (i.e., useable by animals) energy
content and a 3% increase in amino acid
digestibility. Low-stachyose soybeans are
particularly useful for feeding of monogas-
tric animals (swine, poultry, etc.), since their
single stomach cannot digest stachyose.
Thus, stachyose tends to “ferment” (promote
excess bacterial growth) in their intestines,
causing them to feel prematurely full. See
also
STACHYOSE
,
CARBOHYDRATES
  (
SACCHA-
RIDES
),
VALUE
-
ENHANCED GRAINS
,
SOYBEAN
PLANT
,
HIGH
-
SUCROSE SOYBEANS
,
DIGESTION
(
WITHIN ORGANISMS
),
METABOLISM
.
Low-Tillage Crop Production A methodol-
ogy of crop production in which the farmer
utilizes a minimum of mechanical cultivation
(i.e., only two to four passes over the field with
tillage equipment instead of the conventional
five passes per year utilized for traditional crop
production). This reduced mechanical tillage
leaves more carbon in the (less disturbed) soil,
leaves more earthworms (Eisenia foetida) per
cubic foot or per cubic meter living in the
topsoil, and reduces soil compaction (i.e., the
reduction in interstitial spaces between indi-
vidual soil particles); thereby increasing the
fertility of “low till” farm fields.
The plant residue remaining on the field’s
surface helps control weeds and reduce soil
erosion; it also provides sites for insects to
shelter and reproduce, leading to a need for
increased pest insect control via methods
such as inserting a Bacillus thuringiensis
(B.t.) gene into certain crop plants. But if a
farmer needs to apply synthetic chemical
pesticides, the plant residue remaining on
the field’s surface helps cause breakdown
(into substances such as carbon dioxide and
© 2002 by CRC Press LLC

L
water) of those pesticides. That is because
that plant residue helps to retain moisture in
the field-surface environment, thereby
enhancing growth of the types of microor-
ganisms that help break down pesticides. See
also
NO
-
TILLAGE CROP PRODUCTION
,
GLOMALIN
,
EARTHWORMS
,
MICROORGANISMS
,
INTEGRATED
PEST MANAGEMENT
  (
IPM
),
CORN
,
SOYBEAN
PLANT
,
BACILLUS THURINGIENSIS
  (
B
.
t
.),
GENE
,
GENETIC ENGINEERING
,
EUROPEAN CORN BORER
(
ECB
),
HELICOVERPA ZEA
  (
H
.
ZEA
),
CORN ROOT-
WORM
,
COLD HARDENING
.
LOX Null Soybeans Refers to soybeans that
do not contain any of the three lipoxygenase
enzymes (thus, they result in a “null” test
reading). See also 
LIPOXYGENASE
 (
LOX
),
LOX-
1
,
LOX
-
2
,
LOX-
3
,
SOYBEAN PLANT
,
ENZYME
.
LOX-1 One of the isozymes (enzyme mole-
cule variations) of the lipoxygenase (LOX)
enzyme “family.” See also 
LIPOXYGENASE
(
LOX
),
ISOZYMES
 (
ISOENZYMES
).
LOX-2 One of the isozymes (enzyme mole-
cule variations) of the lipoxygenase (LOX)
enzyme “family.” See also 
LIPOXYGENASE
(
LOX
),
ISOZYMES
 (
ISOENZYMES
).
LOX-3 One of the isozymes (enzyme mole-
cule variations) of the lipoxygenase (LOX)
enzyme “family.” See also 
LIPOXYGENASE
(
LOX
),
ISOZYMES
 (
ISOENZYMES
).
LPAAT Protein A protein consisting of lyso-
phosphatidic acid acyl transferase (enzyme),
which (when present in a plant) causes pro-
duction of triglycerides (in the seeds) pos-
sessing saturated fatty acids in the “middle
position” of the triglycerides’ molecular
(glycerol) “backbone.” For example, canola
(rapeseed) plants genetically engineered to
contain LPAAT protein are able to produce
high levels of saturated fatty acids (including
laurate) in their oil. See also 
PROTEIN
,
LAU-
RATE
,
ENZYME
,
TRIGLYCERIDES
,
SATURATED
F A T T Y A C I D S
,
M O N O U N S A T U R A T E D F A T S
,
CANOLA
,
GENETIC ENGINEERING
.
LPE See
LYSOPHOSPHATIDYLETHANOLAMINE
.
LPS See
ENDOTOXIN
.
Luciferase Refers to a group of enzymes that
can catalyze a chemical reaction that results
in the production of light (i.e., biolumine-
scense) within certain living oganisms. For
example, the common firefly is able to emit
light from its tail (photophores) via
luciferase-catalyzed bioluminescence. The
ocean jellyfish known as the sea pansy
(Renilla reniformis) is able to emit light via
similar use of a slightly different luciferase
molecule. See also 
B I O L U M I N E S C E N C E
,
ENZYME
,
CATALYST
,
ORGANISM
,
NITRIC OXIDE
.
Luciferin See
BIOLUMINESCENCE
.
Lumen The interior (opening through which
blood flows); e.g., within a blood vessel. See
also
ENDOTHELIUM
.
Luminesce See
BIOLUMINESCENCE
.
Luminescence See
BIOLUMINESCENCE
.
Luminescent Assays Refers to assays (i.e.,
tests/test techniques) which detect or mea-
sure the presence of a specific substance
(e.g., bacteria ATP on surfaces in a slaugh-
terhouse) and the efficacy (i.e., effective-
ness) of a specific substance via the enzyme
(e.g., luciferase)-catalyzed production of
light. For example, one (rapid) luminescent
assay utilizes two chemical reagents which
first break down bacteria cell membranes,
then cause ATP from those broken-open
cells to luminesce. Subsequent measurement
of that light is the assay’s proof (e.g., that
bacteria had been present on the tested sur-
face in a slaughterhouse). See also 
ASSAY
,
BIOLUMINESCENCE
,
ENZYME
,
BACTERIA
,
PLASMA
MEMBRANE
,
ADENOSINE TRIPHOSPHATE
 (
ATP
).
Lupus An autoimmune disease of the body, in
which anti-DNA antibodies bind to DNA.
The resulting complexes (of DNA and anti-
bodies) travel to the kidneys via the blood-
stream, and become lodged in the kidneys,
where they cause inflammatory reactions
(that can lead to kidney failure). Sometimes
joints, blood vessels, bone marrow, and the
liver are also damaged by this disease. See
also
ANTIBODY
,
DEOXYRIBONUCLEIC ACID
 (
DNA
),
AUTOIMMUNE DISEASE
,
SUPERANTIGENS
.
Lupus Erythematosus See
LUPUS
.
Lutein A carotenoid (i.e., “light harvesting”
compound utilized in photosynthesis) that is
naturally produced in carrots, summer squash,
broccoli, dark lettuce, and green peas. Lutein
is a phytochemical/nutraceutical conducive
to good eye health, and regular consumption
of large amounts of lutein has been shown
to reduce the risk of the disease age-related
macular degeneration, a leading cause of
blindness in elderly people. Research
© 2002 by CRC Press LLC

L
indicates that consumption of lutein by
humans also reduces risk of prostate cancer
and breast cancer. See also 
PHYTOCHEMICALS
,
NUTRACEUTICALS
,
CAROTENOIDS
,
PHOTOSYNTHE-
SIS
.
Luteinizing Hormone (LH) A reproductive
hormone that acts upon the ovaries to stim-
ulate ovulation. It is secreted by the pituitary
gland. See also 
HORMONE
,
PITUITARY GLAND
,
ENDOCRINE HORMONES
,
ESTROGEN
.
Luteolin See
NODULATION
.
Lycopene An antioxidant carotenoid (“light
harvesting” pigment utilized by plants in the
photosynthesis process) that is a naturally
occurring phytochemical in tomatoes, water-
melon, guava, pink grapefruit (and some
other fruits). Consumption of significant
amounts of lycopene by humans causes an
increase in the concentration of lycopene in
the blood plasma. Lycopene is a natural con-
stituent of blood plasma and certain tissues
in the human body, but it must be consumed
in the diet, because the human body does not
synthesize (manufacture) lycopene. Con-
sumption of lycopene by humans has been
linked to a reduction in atherosclerosis, cor-
onary heart disease, some cancers (e.g.,
prostate cancer), and inhibition of oxidation
of low-density lipoproteins (LDLP).
Lycopene is also converted (in some
instances) into alpha-carotene and/or beta-
carotene. Because beta-carotene is pro-
cessed into vitamin A by the human body,
consumption of this phytochemical can help
prevent human diseases (e.g., in developing
countries) that result from deficiency of vita-
min A, e.g.: coronary heart disease; certain
cancers (cancer of prostate, lung, etc.), child-
hood blindness, macular degeneration (a
leading cause of blindness in older people),
and various childhood diseases that can
cause death due to a weakened immune sys-
tem. See also 
PHYTOCHEMICALS
,
NUTRACEUTI-
CALS
,
CANCER
,
ANTIOXIDANTS
,
CAROTENOIDS
,
CORONARY HEART DISEASE
  (
CHD
),
PLASMA
,
ATHEROSCLEROSIS
,
PROSTATE
-
SPECIFIC ANTIGEN
(
PSA
),
TOMATO
,
BETA CAROTENE
,
VITAMIN
,
LUTEIN
,
PHOTOSYNTHESIS
,
LOW
-
DENSITY LIPO-
PROTEINS
 (
LDLP
).