Decarboxylases mechanism-based inactivation

Strauss E, Zhai H, Brand LA, McLafferty FW, Begley TP. Mechanistic studies on phosphopantothenoylcysteine decarboxylase trapping of an enethiolate intermediate with a mechanism-based 33. inactivating agent. Biochemistry 2004 43 15520-15533. 

The enzyme is inactivated by borohydride in the presence of substrate, and acid hydrolysis of the inactivated enzyme yielded e-N-isopropyllysine. Decarboxylation occurs from a Schiff base by a mechanism analogous to that of the aldol cleavage shown in Eq. 13-36.236 Mechanistically related is 4-oxalocrotonate decarboxylase.2363... 

Paracatalytic enzyme modification is a new type of catalysis-linked and, hence, substrate-dependent enzyme modification. In all instances in which the substrate promotes inactivation of an enzyme by a chemical reagent, particularly by an oxidant, paracatalsrtic modification should he considered to be the underlying mechanism. In contrast to ligand-induced and syncatalytic modifications, paracatalytic modification involves a direct chemical interaction between enzyme-activated substrate and extrinsic reagent. In this respect, it is similar to the chemical trapping of covalent enzyme-substrate intermediates, e.g., the reduction of enzyme-substrate Schiff bases by sodium borohydride in class I fructose-l,6-bis-phosphate aldolases - or in acetoacetate decarboxylase. ... 

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