Involvement of two cytosolic enzymes and a novel intermediate, 5'-oxoaverantin, in the pathway from 5'-hydroxyaverantin to averufin in aflatoxin biosynthesis

抄録

In aflatoxin biosynthesis 5'-hydroxyaverantin (HAVN) is converted to averufin (AVR). We demonstrated that this step is composed of two enzymatic steps: an enzyme, HAVN dehydrogenase, catalyzes the reaction from HAVN to a new intermediate and another new enzyme catalyzes the following reaction from the intermediate to AVR. The intermediate was assigned to be 5'-oxoaverantin (OAVN) by spectroscopic methods. We purified HAVN dehydrogenase and OAVN cyclase from the cytosol fraction of A. parasiticus and characterized. MALDI-TOFMS analysis of tryptic peptides of the purified HAVN dehydrogenase revealed that this enzyme is encoded by adhA gene in the aflatoxin gene cluster of A. parasiticus.