PURIFICATION AND PROPERTIES OF QUINOLINATE PHOSPHORIBOSYLTRANSFERASE FROM THE “SHIITAKE” MUSHROOM (LENTINUS EDODES)

Abstract

A considerably high activity of quinolinate phosphoribosyltransferase, an intermediary enzyme in the de novo NAD biosynthetic pathway, was found in a soluble fraction of the “Shiitake” mushroom extract. Highly purified enzyme (approximately 1, 000-fold, chromatography-cally pure) was extracted for the first time from mushrooms and its general properties were investigated. An apparent molecular weight of 1.6×10⁵ was estimated by the gel filtration method. The optimum pH for the reaction was 6.5. The reaction required a divalent cation in addition to quinolinic acid and PRPP. Michaelis constants for quinolinic acid, PRPP and Mg⁺⁺ were 1.1×10^-5 M, 2.3×10^-5M and 2.0×10^-4M, respectively. The reaction product was identified as nicotinic acid mononucleotide by KCN addition reaction and by paper partition chromatography.