AP BIOLOGY

Detailed explanation-1: -PEP is formed by the action of the enzyme enolase on 2-phosphoglyceric acid. Metabolism of PEP to pyruvic acid by pyruvate kinase (PK) generates adenosine triphosphate (ATP) via substrate-level phosphorylation. ATP is one of the major currencies of chemical energy within cells.

Detailed explanation-2: -Phosphorylation of pyruvate kinase results in enzyme inhibition and decreased recycling of phosphoenolpyruvate to pyruvate and enhanced glucose synthesis.

Detailed explanation-3: -Pyruvate kinase catalyzes the direct transfer of phosphate from phosphoenolpyruvate (PEP) to ADP to produce ATP and pyruvate.

Detailed explanation-4: -There are two steps in the pyruvate kinase reaction in glycolysis. First, PEP transfers a phosphate group to ADP, producing ATP and the enolate of pyruvate. Secondly, a proton must be added to the enolate of pyruvate to produce the functional form of pyruvate that the cell requires.

Detailed explanation-5: -Like many other proteins, human liver pyruvate kinase (hL-PYK) is regulated by phosphorylation. The phosphorylation of hL-PYK occurs on Ser12 of the N-terminus. Phosphorylation appears to interrupt an interaction (distant from the active site) between the N-terminus and the main body of the protein.