GLOSSARY

Branched-Chain Amino Acid Aminotransferase (BCAT) catalyzes branched-chain amino-acid transamination.

Transamination transfers amino groups rather than necessarily releasing ammonia directly. Deamination, deamidation and amination handle different groups or directions. Ammonia and ammonium are acid-base-related forms. Transport and disposal systems regulate nitrogen. Exercise fatigue alone does not establish dangerous ammonia accumulation or a self-treatment need. Distinguish reaction chemistry from a clinical disorder, and assess context rather than equating every nitrogen-containing metabolite with harmful waste or every aminating step with muscle growth.

Amino acids support proteins and other compounds, while carbon skeletons can enter energy pathways after nitrogen handling. There is no unlimited dedicated amino-acid store comparable to fat storage. Oxidation of some protein does not prove total intake inadequate or unlimited extra intake builds more muscle. Athletes need total amount, quality, distribution and adequate energy alongside training load. Carbon fate, nitrogen disposal and protein synthesis are separate processes rather than one simple anabolic-versus-waste label.

A cofactor is a nonprotein component needed by some enzymes and may be an inorganic ion or an organic molecule. A coenzyme is organic, while a prosthetic group is generally tightly associated. Apoenzyme denotes protein lacking a required cofactor, and holoenzyme the complete active form. Binding strength and role must be specified: not every substance near an enzyme is its essential cofactor.

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.

Measured activity is conversion per time under assay conditions rather than simply protein abundance. A substrate-rich assay may reveal potential capacity, while living tissue has different constraints and regulation. Units, tissue normalization and preparation methods are needed for comparison. Blood activity is not identical to intramuscular activity; laboratory changes require exercise timing, symptoms and tissue origin rather than being read as direct performance measures or a standalone diagnosis.

Training can change enzyme abundance, regulation or activity capacity depending on mode, intensity, volume and training history. An acute session response is not the same as chronic adaptation. Oxidative or glycolytic markers describe only part of performance; oxygen delivery, fuel stores and neural coordination also matter. Practical assessment therefore combines performance and recovery outcomes with adequate nutrition and the actual training program rather than relying on one enzyme marker.