GLOSSARY

Enzyme Turnover in kinetics concerns catalytic cycling, distinct from protein renewal.

Michaelis–Menten describes simplified initial-rate behavior under appropriate assumptions and conditions. Many allosteric enzymes and multisubstrate reactions require more than this simple model. Saturation means further substrate addition no longer produces a proportional rate increase; it does not mean bodily stores are full. Laboratory data need temperature, pH and enzyme concentration reported, and model parameters should not be transferred unchanged to intact exercising tissue.

In the simple model, Km is the substrate concentration giving half Vmax; it is not generally a binding dissociation constant. It reflects several microscopic rates, so lower Km does not universally mean tighter binding. Enzyme comparisons require compatible substrates and methods. A laboratory Km cannot by itself calculate an athlete's required food portion or target blood concentration, because cellular transport, compartmentation and pathway control also intervene.

Vmax depends on active enzyme amount and assay conditions; kcat expresses saturated turnover per active site. The kcat/Km ratio characterizes efficiency within the model, particularly at low substrate concentration. Substrate, product and enzyme concentrations have different roles. A higher enzyme parameter alone does not establish faster whole-body metabolism or superior performance; measurement boundaries, units and the distinction between potential capacity and actual flux remain essential.

A double-reciprocal plot can illustrate patterns, but reciprocal transformation can amplify errors at low substrate concentrations. Direct fitting of a suitable model to original data is generally preferable for parameter estimation. A neat straight line does not prove a unique mechanism; concentration range, replication and alternative models matter. Plot slopes have defined units and interpretations and are not measures of an individual's sports efficiency or nutritional requirement.

Cooperativity means that binding or state in one part affects another part's behavior. Positive and negative describe the direction of that effect rather than health benefit or harm. A Hill coefficient is an empirical response-slope measure, not necessarily an exact count of binding sites. Sigmoidal and hyperbolic responses differ, but curve shape alone cannot identify every molecular step or establish a complete regulatory mechanism.

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.