Properties of a glucosyltransferase involved in crocin synthesis

The properties of a partially purified uridine-5'-diphosphoglucose (UDP-glucose)- crocetin 8,8'-glucosyltransferase (EC 2.4.1.) involved in crocin synthesis are described. The enzyme participates in the biosynthesis of crocin by forming ester bonds between the carboxyl groups of crocetin and the glucose moiety of UDP-glucose. The enzyme has been purified 125-fold trough a multi-step process of acetone fractionation, anion-exchange, and gel filtration chromatography. The native molecular weight is in the range of 47 kDa, as estimated by analytical gel filtration. The most purified preparation showed isoforms between pH 4.4 and 4.8 when resolved by IEF. The enzyme had maximal activity at 40 degrees C, apparent K-m values for UDP-glucose and crocetin were 0.72 and 0.17 mM, respectively, and V-max, 30 pkatal/mg. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.