Polyhydroxynaphthalene reductase involved in melanin biosynthesis in Magnaporthe grisea Purification, cDNA cloning and sequencing

Abstract

During the biosynthesis of fungal melanin, tetrahydroxynaphthalene reductase catalyzes the NADPH‐dependent reduction of 1,3,6,8‐tetrahydroxynaphthalene (T4HN) into (+)‐scytalone and 1,3,8‐trihydroxynaphthalene into (–)‐vermelone. The enzyme from Magnaporthe grisea, the fungus responsible for rice blast disease, has been purified to homogeneity. It is a tetramer of four identical 30‐kDa subunits. A full‐length cDNA clone of about 1 kb encoding T4HN reductase has been isolated from a cDNA library constructed in the λZAP II vector and characterized. The clone contains a 846‐bp open reading frame. Translation of the DNA sequence gave a 282‐residue amino acid sequence with a calculated molecular mass of 29.9 kDa. Sequences corresponding to the amino‐terminal part and three internal proteolytic peptides were present in the translated sequence. T4HN reductase exhibits characteristics of the short‐chain alcohol dehydrogenase family. The reductase shares 56% identity with a putative ketoreductase involved in aflatoxin biosynthesis in Aspergillus parasiticus. Copyright © 1994, Wiley Blackwell. All rights reserved