Ketohexokinase (ATP: d-fructose 1-phosphotransferase) initiates fructose breakdown via the modified EMP pathway in halophilic archaebacteria

Abstract

Abstract Ketohexokinase, catalysing the ATP-dependent phosphorylation of D -fructose to fructose 1-phosphate was identified as the enzyme responsible for the initiation of fructose breakdown via the modified EMP pathway in the halophilic arachaebacterium Haloarchla vallismortis . The phosphorylated product was identified as fructose 1-phosphate through its conversion to (i) a biphosphate ester by H. vallismortis 1-phosphofruktokinase, and (ii) trioses by rabbit muscle aldolase. The product of ketohexokinase reaction gave glyceraldehyde and dihydroxyacetone phosphate when cleaved directly by mammalian muscle aldolase, whereas, glyceraldehyde 3-phosphate and dihydroxyacetone phosphate were produced when it was converted to the biphosphate ester prior to the treatment with aldolase. This is a first demonstration of ketohexokinase not only in an arachaebacterium but also in a prokaryote.