GLOSSARY

Enzyme Isoform is a molecular variant, a broader term than isoenzyme.

Isoenzymes are molecularly different forms catalyzing the same reaction, potentially differing in tissue distribution or regulation. Isoform is a broader molecular-variant term and is not always an exact synonym. A circulating form does not directly establish the quantity or activity of the corresponding enzyme inside muscle. Assay method and tissue origin matter when interpreting laboratory findings or exercise research and comparing different samples.

Enzyme abundance reflects protein synthesis and degradation; gene expression, RNA, protein quantity and measured activity are different layers. Induction and repression need definition because expression and activity can differ. Constitutive does not mean a perfectly constant amount under all conditions. In exercise interpretation, long-term capacity changes must be separated from rapid activation of existing enzyme and from actual pathway flux rather than treating them as interchangeable findings.

Location determines access to substrates, cofactors and local conditions. Cytosol, mitochondrial matrix, peroxisomes and nucleus are not equivalent environments. Microsomal usually refers to a laboratory membrane fraction largely derived from endoplasmic reticulum, not a normal independent organelle in living cells. Direct transfer of intermediates between enzymes requires evidence; proximity or membership of the same compartment alone does not establish substrate channeling or its magnitude.