Enzyme international units – quantity of enzyme that catalyzes the conversion of
1. µmol of substrate per minute. Factors Affecting Enzyme Activity. •Presence of ...
Enzyme Activity
Enzyme Activity
Rate at which an enzyme catalyzes a reaction. Studied in experiments called enzyme assays to determine: – Turnover number – number of substrate molecules acted on by one enzyme molecule per minute. – Enzyme international units – quantity of enzyme that catalyzes the conversion of 1 µmol of substrate per minute.
Factors Affecting Enzyme Activity •Presence of cofactors, inhibitors, modulators and zymogen activation agents •Presence of heavy metals (Pb, Cd, Hg…) resulting in metal sulfide complexes interrupting the disulfide bridges, ultimately resulting in denaturation of the native state.
Factors Affecting Enzyme Activity, Con’t. • pH – enzymes have optimum pHs, above and below which the rate decreases.
•Change in pH of the environment results in a change in the rate of catalysis Denatured
Factors Affecting Enzyme Activity, Con’t. • Enzyme concentration – the more enzyme present, the faster substrate reacts.
Factors Affecting Enzyme Activity, Con’t. • Increasing substrate concentration – increases the reaction rate until enzymes become saturated (Vmax).
•Enzyme concentration does not affect the concentration of reactant or products, only rate of reaction
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Factors Affecting Enzyme Activity, Con’t. • Temperature – enzymes have an optimum temperature, above which they begin to denature.
Enzymes of the Gastrointestinal Track (Digestive System) Enzyme
Catalyzes
Activation
Mouth: •Amalyase
Enzyme
saliva
proteins
H+
Stomach:
Biological activity maximum is between 33 and 42oC
•Peptidases
starches
•Pepsin
Pancreas/ Sm. Intestine: •Lipases
Catalyzes
Activation
proteins
Trypsin
Autoactivated
Chymotrypsin
Trypsin
Carboxypeptidase
Trypsin
Trypsin, pepsin, and chymotrypsin all cleave peptide bonds in proteins and are endopeptidases
Antibiotics •Penicillin Inhibitor that inhibits the formation of structurally sound cell walls in bacteria Since humans lack cell walls, it does not inhibit human enzyme functions Penicillin along with its derivatives are used to slow bacteria growth until our body’s defenses can take on the attacker.
lipids
Autoactivation
•Endopeptidases catalyze the hydrolysis of peptide bonds on interior amino acid residues but not terminal residues.
•Enzymes that hydrolyze terminal amino acid residues are called exopeptidases.
Medical Applications • Changes in blood serum concentrations of specific enzymes can be used to detect cell damage or uncontrolled growth (cancer). • The measurement of enzyme concentrations in blood serum has become a major diagnostic tool, particularly in diagnosing diseases of the heart, liver, pancreas, prostate, and bones.
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Medical Applications, cont.
Medical Applications, cont. • Isozymes are slightly different forms of the same enzyme produced by different tissues. • Serum levels of isozymes can be used in the diagnosis of a wide range of diseases.
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