Isozyme

isoenzymeisozymesisoenzymesisoformsformCOX-isozymeformsisoenzymaticisozyme fingerprintsisozyme studies
Isozymes (also known as isoenzymes or more generally as multiple forms of enzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction.wikipedia
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Enzyme

enzymologyenzymesenzymatic
Isozymes (also known as isoenzymes or more generally as multiple forms of enzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction.
Different enzymes that catalyze the same chemical reaction are called isozymes.

Clement Markert

Clement L. Markert
Isozymes were first described by R. L. Hunter and Clement Markert (1957) who defined them as different variants of the same enzyme having identical functions and present in the same individual.
Clement Lawrence Markert (April 11, 1917 – October 1, 1999) was an American biologist credited with the discovery of isozymes (different forms of enzymes that catalyze the same reaction).

Alloenzyme

allozymeallozymesalloenzymes
Although, strictly speaking, allozymes represent enzymes from different alleles of the same gene, and isozymes represent enzymes from different genes that process or catalyse the same reaction, the two words are usually used interchangeably.
These are opposed to isozymes, which are enzymes that perform the same function, but which are coded by genes located at different loci.

Glucokinase

GCKMODY2
An example of an isozyme is glucokinase, a variant of hexokinase which is not inhibited by glucose 6-phosphate.
Glucokinase (GK) is a hexokinase isozyme, related homologously to at least three other hexokinases.

Hexokinase

Hexokinase IVhexokinase-2
An example of an isozyme is glucokinase, a variant of hexokinase which is not inhibited by glucose 6-phosphate.
Several hexokinase isoforms or isozymes that provide different functions can occur in a single species.

Lactate dehydrogenase

LDHlactic acid dehydrogenaselactic dehydrogenase
1.) The enzyme lactate dehydrogenase is a tetramer made of two different sub-units, the H-form and the M-form.

Michaelis–Menten kinetics

Michaelis-Menten kineticsMichaelis-MentenK m
These enzymes usually display different kinetic parameters (e.g. different K M values), or different regulatory properties.

Biochemistry

biochemistbiochemicalbiological chemistry
In biochemistry, isozymes (or isoenzymes) are isoforms (closely related variants) of enzymes.

Homology (biology)

homologoushomologyhomolog
In many cases, they are coded for by homologous genes that have diverged over time.

Gene

genesnumber of genesgene sequence
Although, strictly speaking, allozymes represent enzymes from different alleles of the same gene, and isozymes represent enzymes from different genes that process or catalyse the same reaction, the two words are usually used interchangeably.

Catalysis

catalyzescatalysescatalyst
Although, strictly speaking, allozymes represent enzymes from different alleles of the same gene, and isozymes represent enzymes from different genes that process or catalyse the same reaction, the two words are usually used interchangeably.

Locus (genetics)

locuslociq arm
This definition encompasses (1) enzyme variants that are the product of different genes and thus represent different loci (described as isozymes) and (2) enzymes that are the product of different alleles of the same gene (described as allozymes).

Allele

allelesallelicmultiple alleles
Although, strictly speaking, allozymes represent enzymes from different alleles of the same gene, and isozymes represent enzymes from different genes that process or catalyse the same reaction, the two words are usually used interchangeably. This definition encompasses (1) enzyme variants that are the product of different genes and thus represent different loci (described as isozymes) and (2) enzymes that are the product of different alleles of the same gene (described as allozymes).

Gene duplication

duplicationduplicationsamplification
Isozymes are usually the result of gene duplication, but can also arise from polyploidisation or nucleic acid hybridization.

Polyploidy

tetraploidpolyploidtriploid
Isozymes are usually the result of gene duplication, but can also arise from polyploidisation or nucleic acid hybridization.

Nucleic acid hybridization

hybridizationDNA hybridizationhybridize
Isozymes are usually the result of gene duplication, but can also arise from polyploidisation or nucleic acid hybridization.

Mutation

mutationsgenetic mutationmutated
Over evolutionary time, if the function of the new variant remains identical to the original, then it is likely that one or the other will be lost as mutations accumulate, resulting in a pseudogene. Allozymes may result from point mutations or from insertion-deletion (indel) events that affect the coding sequence of the gene.

Pseudogene

pseudogenespseudogenizationpseudo genes
Over evolutionary time, if the function of the new variant remains identical to the original, then it is likely that one or the other will be lost as mutations accumulate, resulting in a pseudogene.

Gene expression

expressionexpressedexpress
However, if the mutations do not immediately prevent the enzyme from functioning, but instead modify either its function, or its pattern of expression, then the two variants may both be favoured by natural selection and become specialised to different functions.

Natural selection

selectionselectiveselected
However, if the mutations do not immediately prevent the enzyme from functioning, but instead modify either its function, or its pattern of expression, then the two variants may both be favoured by natural selection and become specialised to different functions.

Point mutation

point mutationsbase-pair substitutionsubstitution
Allozymes may result from point mutations or from insertion-deletion (indel) events that affect the coding sequence of the gene.

Amino acid

amino acidsresiduesresidue
In particular, amino acid substitutions that change the electric charge of the enzyme are simple to identify by gel electrophoresis, and this forms the basis for the use of isozymes as molecular markers.

Neutral theory of molecular evolution

neutralneutral evolutionneutral theory
However, such differences are usually subtle, particularly between allozymes which are often neutral variants.