PYRIDOXAL 5'-PHOSPHATE-DEPENDENT CATALYTIC ANTIBODY

Cofactors might efficiently extend the catalytic potential of antibodi es. Monoclonal antibodies against N-alpha-phosphopyridoxyl-L-lysine we re screened for: 1) binding of 5'-phosphopyridoxyl amino acids, 2) bin ding of Schiff base of pyridoxal 5'-phosphate (PLP) and amino acids, t he first intermediate of all PLP-dependent reactions, and 3) catalysis of PLP-dependent alpha,beta-elimination with beta-chloro-D/L-alanine. All three criteria were met by antibody 15A9. Further analysis for PL P-dependent reactions showed that this antibody catalyzes the cofactor -dependent transamination of hydrophobic D-amino acids and oxo acids ( k(cat) = 0.42 min(-1) with D-alanine). No other reactions with either D- or L-amino acids were taking place. PLP markedly contributes to cat alytic efficacy, being a 10(4) times more efficient acceptor of the am ino group than pyruvate. The antibody further accelerates the reaction (k'(cat(antibody))/k'(cat(PLP)) = 5 x 10(3) with D-alanine as substra te) and ensures reaction specificity, stereospecificity, as well as li mited substrate specificity.