Alkaline phosphatase essential groups

Enzymes are protein catalysts of remarkable efficiency and specificity. Lipid, carbohydrate, nucleotide, or metal-containing prosthetic groups may be attached to these enzymes and serve as essential components of their catalyses by enhancing specificity and/or stability (8—13). Each enzyme has a specific temperature and pH range where it functions to its optimal capacity the optima for these proteins usually He between 37—47°C, and pH optima range from acidic, ie, 1.0 in the case of gastric pepsin, to alkaline, ie, 10.5 in the case of alkaline phosphatase. However, enzymes from extremely thermotolerant bacteria have become available these can function at or near the boiling point of water, and therapeutic use of these ultrastable proteins can be anticipated. 

The enzymes used to generate reactive quinone methides often undergo inactivation by addition of this electrophile to essential nucleophilic amino acid side chains of the protein catalyst. This is a type of suicide enzyme inhibition.80 This was observed for the acid phosphatase and ribonuclease catalysts used to generate 43.76 79 Alkaline phosphatase has been used to remove the phosphate protecting group from a derivative of an o-difluoromethyl phenyl phosphate that was covalently attached to a solid support. Breakdown of the immobilized 4-hydroxybenzyl difluoride gives an immobilized quinone methide that, in principle, will react irreversibly with proteins and lead to their attachment to the solid support.81... 

In our view, iodine inactivation in the case of rat intestinal alkaline phosphatase causes blocking of the —SH group, since other evidence for the presence of this group is strong. The c-amino group of lysine is considered to be essential not merely because tyrosine can be reasonably excluded, but because rat intestinal alkaline phosphatase is inhibited by the lysine-specific o-methylisourea reagent and because the pZm-pH plot shows a discontinuity at pH 9.6 (G5), the pilf of the e-amino group of lysine (C14). 

Finally, the imidazole group has not been found to be essential for alkaline phosphatase (P9). 

A regioselective dephosphorylation was used in the synthesis of 2 -carboxy-D-arabinitol 1-phosphate (Table 13-6, entry 2), a natural inhibitor of ribulose 1,5-bisphosphate carboxylase. Either acid or alkaline phosphatases can be used for the selective hydrolysis of the 1-phosphoryl group of 2 -carboxyl-D-arabinitol 1,5-bisphosphate. With acid phosphatase, the conversion was essentially quantitative yielding exclusively the 1-phosphate derivative (cleavage of the 5-phosphoryl group). On the other hand, hydrolysis with alkaline phosphatase gave a 4 1 mixture of the 1-and 5-phosphate derivatives. 

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