Enzyme with arsenate acceptor

The mode of action of sucrose phosphorylase explains the observed role of arsenate in causing the hydrolytic decomposition of both sucrose and a-D-glucose 1-phosphate in the presence of the enzyme (195). Arsenate presumably acts as a D-glucose acceptor with the enzyme, to form an unstable D-glucose 1-arsenate compound, which hydrolyzes spontaneously to D-glucose and arsenate ... 

Arsenate, which can apparently serve as glucose acceptor to the enzyme-D-glucose complex but which does not form a stable glucose ester, causes the rapid decomposition of both sucrose and D-glucose-l-phosphate in accordance with the following equations 44... 

Arsenate can act as an acceptor with P-enzyme, but D-glucose is the product. It is believed that a-D-glucosyl arsenate is formed initially, and that this is imstable and decomposes. The extent of arsenolysis of amylopectin is about the same as that of jS-amyloIysis (55-70%), although, in other experiments, the latter was about 15% more than the degree of... 

Like the Arr of C. arsemtis, the synthesis of the Desulfomicrobium sp. str. Ben-RB arsenate reductase appears to be regulated (9). The highest enzyme activity (100%) was detected when the organism was grown with sulfate and arsenate (0.192 U/mg protein). When grown with sulfate alone as the terminal electron acceptor only 11% of the total activity was detected (0.021 U/mg protein). 

It was at this state of knowledge that an incidental observation with extracts of C. kluy-veri led to a development which played a significant role in elucidating the mechanism of CoA action. It was observed that arsenate inhibited the ability of extracts to catalyze the oxidation of butyrate, as well as the reduction of acetyl-P and acetate to butyrate. The inhibition was ultimately explained by the fact that arsenate stimulated the enzymic hydrolysis of acetyl-P [reaction (18)]. By analogy to the postulated role of arsenate in the hydrolysis of glucose-l-P by sucrose phosphorylase,< > it was proposed that the arsenolysis of acetyl-P could be the result of a reversible transfer of the acetyl moiety to an acetyl acceptor, x , catalyzed by a phosphotransacetylase [reaction (21)]. 

---