labile The term has loosely been used to describe
either a relatively unstable and transient chemical
species or a relatively STABLEbut reactive species.
See alsoINERT.

lability Instability; refers to a state that is easily
altered or modified. A phenotype’s capacity to respond
differentially to varying environmental conditions. Also
called phenotypic plasticity.

laccase A copper-containing ENZYME, 1,4-benzenedi-
ol oxidase, found in higher plants and microorganisms.
Laccases areMULTICOPPER OXIDASESof wide specificity
that carry out one-electron oxidation of phenolic and
related compounds and reduce O 2 to water. The
enzymes are polymeric and generally contain one each
of TYPE1, TYPE2, TYPE 3 COPPERcenters per SUBUNIT,
wherethe type 2 and type 3 are close together, forming
a trinuclear copper CLUSTER.
See alsoNUCLEARITY.

lactate Alternate name for lactic acid, a chemical cre-
ated from sugars when broken down for energy in the
absence of oxygen.

lacteal Numerous small lymphatic vessels in the inte-
rior of each intestinal villus, small fingerlike projections

of the mucosal layer of the small intestine, that

picks up chyme, a thick semifluid mass of partially

digested food, and passes it through the lymph system

via the thoracic duct to the blood system; aids in the

absorption of fats.

lactoferrin An iron-binding protein from milk, struc-

turally similar to the TRANSFERRINs.

lagging strand In DNA synthesis, polymerization

occurs both in and away from the nearest replication

fork. One of two newly created DNA strands is the lag-

ging strand. Found at the replication fork on linear

chromosomes, it is synthesized in the direction away

from the replication fork. It is the synthesis of a new

strand of replication DNA by the creation of short seg-

ments of various lengths that are later joined together

covalently by the enzyme DNA ligase.

It is made in discontinuous lengths, called Ozark

fragments, in the 5’ to 3’ growing-tip (number of atoms

in the sugar residues) direction during DNA polymer-

ization, and these are joined covalently at a later time.

Since it is not synthesized continuously, it is called dis-

continuous replication.

The difference between the lagging and leading

strands is due to the orientation of the parent template

strands. The leading-strand template is facing a 5’ to 3’

direction, but the lagging strand itself is oriented in the

3’ to 5’ direction, so the DNA polymerase responsible

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