A histidine was determined to be the critical residue involved in an enzyme-catalyzed reaction. If the pKa of the histidine is known to be 6.5 in the active site and the pH of maximum catalytic activity is 7.2, what is likely the primary role of histidine in the catalytic reaction? A. forms a covalent bond with the substrate B. reduces the entropy of the substrate C. stabilizes a charged intermediate D. acts as a proton donor Aspartate and lysine are in the active site of an enzyme. They are both known to participate directly in catalysis. The pKa's of the residues are found to be 3.2 and 9.6, respectively for aspartate and lysine. The optimum pH for the enzyme is 6.4. Which forms of these two residues will predominate when the enzyme is most active? A. aspartate is protonated; lysine is deprotonated B. both residues are deprotonated C. aspartate is deprotonated; lysine is protonated D. both residues are protonate
Enzyme kinetics
In biochemistry, enzymes are proteins that act as biological catalysts. Catalysis is the addition of a catalyst to a chemical reaction to speed up the pace of the reaction. Catalysis can be categorized as either homogeneous or heterogeneous, depending on whether the catalysts are distributed in the same phase as that of the reactants. Enzymes are an essential part of the cell because, without them, many organic processes would slow down and thus will affect the processes that are important for cell survival and sustenance.
Regulation of Enzymes
A substance that acts as a catalyst to regulate the reaction rate in the living organism's metabolic pathways without itself getting altered is an enzyme. Most of the biological reactions and metabolic pathways in the living systems are carried out by enzymes. They are specific for their works and work in particular conditions. It maintains the best possible rate of reaction in the most stable state. The enzymes have distinct properties as they can proceed with the reaction in any direction, their particular binding sites, pH specificity, temperature specificity required in very few amounts.
A histidine was determined to be the critical residue involved in an enzyme-catalyzed reaction. If the pKa of the histidine is known to be 6.5 in the active site and the pH of maximum catalytic activity is 7.2, what is likely the primary role of histidine in the catalytic reaction?
A. forms a covalent bond with the substrate
B. reduces the entropy of the substrate
C. stabilizes a charged intermediate
D. acts as a proton donor
Aspartate and lysine are in the active site of an enzyme. They are both known to participate directly in catalysis. The pKa's of the residues are found to be 3.2 and 9.6, respectively for aspartate and lysine. The optimum pH for the enzyme is 6.4. Which forms of these two residues will predominate when the enzyme is most active?
A. aspartate is protonated; lysine is deprotonated
B. both residues are deprotonated
C. aspartate is deprotonated; lysine is protonated
D. both residues are protonated
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