Select the statements that correctly describe pyridoxal phosphate (PLP). Pyridox
ID: 510747 • Letter: S
Question
Select the statements that correctly describe pyridoxal phosphate (PLP). Pyridoxal phosphate is a derivative of pyridoxine. Pyridoxal phosphate can convert an L-amino acid to a D-amino acid. Pyridoxal phosphate acts as an electron sink, stabilizing the reactive intermediate. Pyridoxal phosphate binds covalently to the active site on the enzyme through the formation of a Schiff base. Pyridoxal phosphate is the prosthetic group for all aminotransferases. Pyridoxal phosphate plays an important role in amino group metabolism. Pyridoxal phosphate only participates in reactions at the beta and gamma carbons of amino acids.Explanation / Answer
Pyridoxal phosphate functions as an intermediate carrier of amino groups at the active site of arninotransferases. It undergoes reversible transformations between its aldehyde form, pyridoxal phosphate, which can accept an amino group, and its aminated form, pyridoxamine phosphate, which can donate its amino group to an -keto acid. Pyridoxal phosphate is generally bound covalently to the enzyme's active site through a Schiff base to the -amino group .
Pyridoxal phosphate is involved in a variety of reactions at the and carbons of amino acids. Reactions at the a carbon include racemizations (interconverting L- and D-amino acids) and decarboxylations, as well as transaminations. Pyridoxal phosphate plays the same chemical role in each of these reactions. One of the bonds to the a carbon is broken, removing either a proton or a carboxyl group and leaving behind a free electron pair on the carbon. This intermediate is very unstable and normally would not form at a significant rate. Pyridoxal phosphate provides a highly conjugated structure that permits delocalization of the negative charge, stabilizing the carbanion.
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