GLOSSARY

Enzyme Repression reduces expression rather than directly inhibiting existing enzyme.

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.

Adding or removing a chemical group can alter enzyme activity, location, stability or interactions. Phosphorylation is not universally activating; direction depends on protein and site. Acetylation, methylation and small-protein attachment have varied roles and are not all degradation labels. Post-translational changes must be distinguished from new protein production because their speed and persistence can differ, even when they influence the same pathway or exercise response.

Flux control is usually distributed across steps, substrate supply and demand. Rate-limiting is condition-dependent rather than identifying an enzyme that always commands the whole pathway. A committed step marks more specific entry into a pathway and need not carry the greatest control. Increasing one enzyme or supplying its precursor does not guarantee greater network flux or performance without considering the wider system.