Chemical and mass spectral studies of 2,2-dialkylglycine decarboxylase

Abstract

2,2-Dialkylglycine Decarboxylase, DGD, is a decarboxylating transaminase that is dependent on a vitamin B6 cofactor, pyridoxal 5'-phosphate (PLP). DGD catalyzes the decomposition of 2-methylalanine in two steps. DGD was purified by ammonium sulfate precipitation and ion-exchange chromatography. The enzyme was reduced to form a covalent bond between the enzyme and the PLP. Also, [alpha]-(Trifluoromethyl) Alanine, a suicide mechanism based inhibitor was reacted with DGD until the enzyme was completely inactivated. The nonmodified DGD and these two modified forms of the enzyme were subjected to enzymatic digestion by trypsin. Finally, all three peptide mixtures were analyzed by LC/MS/MS. The mass spectra confirmed the amino acid sequence as predicted by the nucleotides of the gene, and the covalent attachment of the cofactor to lysine 272.