Pyridoxal-P (PLP) is an obligate cofactor for a variety of enzyme-catalyzed transformations at the a,@, y, or o carbons of amino acid substrates by facilitated formation of stabilized substrate carbanion intermediates in catalysis. The subset of enzymes catalyzing y replacement of a potentially good leaving group Y by an alternate nucleophile Y'(eq l), a formal substitution at an unactivated carbon, in fact acts via sequential for-mation of a and ...
