Flashcards in Enzymes Deck (31)
Consist only of proteins (ser=one a.a.)
Bound to enzymes.
-Metal ions (ion-sulfur clusters, Zn, carbonic anhydrase)
Intermed. carrier of e-, specific atoms or funct.gr.
-Water sol. vit. derivates (NAD+, PALP, TPP)
Tightly bound organic cofactors
Hydrolyse peptide bonds of proteins
Major enzymes prod. by pancreas
Substrate binding site of Chymotrypsin
Substrate binding site of Trypsin
Substrate binding site of Elastase
Inhibition of ser-proteases
At Ser-195 by diisopropylphospho-fluoridate DIPF
Mechanism of enzyme action
E+S ES E+P
Free energy between initial and transitional state
Factors affecting enzyme activitiy
-Non-specific: affecting velocity at each enzymatic reaction (temp, pH, denaturation)
-Specific: affecting only certain Es/certain groups of Es (conc. of reactants, inorganic effectors, organic effectors)
Michaelis constant - Km
Km is the substrate conc. at which the velocity of the reaction is half the max. value -> the E is saturated in 50% by substrate.
-Non-specific -> denaturation: acid&bases, temp., alcohol, heavy metals, red. agents
1.Irreversible: Ser-proteases, SH-containing E´s (heavy metals), cytochrome oxidase (CN-ions)
2.Reversible: bound to other than S-site
a)Competetive: sim. as S, bound to S-binding site
B)Non-competetive: bound to another part of the E. Allosteric, feedback
Controlling enzyme action
1. Regulation of its conc. by repressing/inducing its synthesis
2. Red. by inhibitors/incr. by effectors: allosteric phosphorylation, zymogen, isoenzymes, modulator proteins (CAP)
Turning on of transcription = incr. mRNA prod.
Turning off of transcription = drcr. mRNA prod.
The molec. bind to an allosteric site, sep. from the active site, and inhib./stim. the enzyme activity
A type of allosteric regulation. The final product is an allosteric inhib. of the first enzyme in the pathway.
Covalent modification of an enzyme, by addition of a specific funct. gr. -> activate/inhib. the enzyme
Covalent modification of an enzyme.
-Zymogen=proenzyme; inactive precursor form of enzyme
-Activation site=site of cleavage
-Activated by specific regulatory protease
Differ slightly in aa. sequence and consequently in catalytic properties. Have diff. Km.
-Isoform A: high Km-works best in tissues w. high S-conc.
-Isoform B: low Km-works best in tissues w. low S-conc.
One oxidiced, one reduced
Hydrolytic cleavage of diff. bonds.
Elimination/addition, without breakdown of ATP