The Structure of Extracellular Phosphorylated Galactans from Sporobolomyces Yeasts

Abstract

Two strains of SporoboZomyces species, NRRL Y-6493 and NRRL Y-6502, produce extracellular, lightly acetylated, phosphorylated galactans when grown on media containing glucose as the carbon source.D-&lactose and D-galactose 6-phosphate were the only carbohydrate components present in strong acid hydrolysates.oc-D-Galactose 1 -phosphate was isolated after vigorous alkaline hydrolysis.Periodate oxidation analyses of intact and deacetylated polymers indicate that approximately equal proportions of a-1,6-and a-1,3galactosyl linkages are present.Polymer phosphate occurs exclusively in the form of cy-n-galactopyranosyl-l-phospho-6'-galactosyl phosphodiester end groups.Earlier work from the Northern Laboratory described a series of extracellular phosphorylated mannans produced by yeasts of the genus Hansen& and related genera (1, 2).A characteristic structural feature of the "phosphomannans" is the cY-n-mannosyl-1-phospho-6'-mannose phosphodiester bridge (3, 4).Hydrolysis of these polymers in strong acid yields n-mannose and n-mannose 6-phosphate.This work describes the isolation and structural characterization of analogous "phosphogalactans" from culture filtrates of certain Sporobolomyces yeasts grown on glucose.The phosphate of these partially acetylated polymers occurs in the form of the oL-n-galactopyranosyl-1-phospho-6'-galactosyl Strong acid hydrolysis of phosphogalactans and n-galactose 6-phosphate.phosphodiester.yields n-galactose MATERIALS AND METHODS Production and Isolation of Polymers-The organisms Xporobolomyces species NRRL Y-6493 and NRRL.Y-6502 were collected in 1963 by Dr. L. J. Wickerham in the vicinity of Amherst, Massachusetts.Polymer production from glucose in shaken flask cultures at 25" and an oxygen absorption rate >0.5 (5) depended markedly upon nitrogen source and inoculum age.The medium contained Vito D-2001 autolyzed brewers' 1 The mention of firm names or trade products does not imply that they are endorsed or recommended by the Department of Agriculture over other firms or similar products not mentioned.