Cofactor-dependence of phosphoglycerate mutase activity in a variety of fungi

Abstract

Phosphoglycerate mutase catalyses the interconversion of 2and 3phosphoglycerates. The enzyme has been purified from a variety of sources including baker's yeast [1,2], rabbit muscle [3] and wheat germ [4]. From a survey of a number of different tissues, Grisolia and Joyce [5] concluded that the enzyme from plant sources was active in the absence of added 2,3-bisphosphoglycerate (BPG), whereas that from mammalian yeast and bacterial sources was inactive in the absence of this cofactor. A more recent paper [6] suggests that BPG-independent mutases are not confined to plant sources, although few details are given. The enzymes from yeast and rabbit muscle are tetrameric and dimeric respectively [3] whereas that from wheat germ is a monomer [4]. During an investigation of phosphoglycerate mutase in Aspergillus nidulans we noted that the activity was independent of added BPG. This prompted a study of the cofactor-dependence of the enzyme in a variety of other fungi and in the cellular slime mould Dictyostelium discoideum. The phosphoglycerate mutase in all the filamentous fungi studied is independent of BPG, whereas that in three different species of yeasts and in D. discoideum shows cofactor dependence. A. nidulans BWB 272 is from the Glasgow strain. Mucor plumbeus, Trichoderma viride, Penicillium expansum, Chaetomium globosum, Phlebia merismoides and Pythium acanthium were obtained from Dr. N. Dix (Stifling University, Biological Science Department). Phycomyces blakesleeanus (CMI 63219), Rhizopus stolonifer (CMI 57762, Saccharomyces cerevisiae (Fleischmann) (CMI 19391), Candida utilis (CMI 23311) and Schizosaccharomyces pombe (CMI 39917) were obtained from the Commonwealth Mycological Institute (Kew, Surrey, England). Dried baker's yeast was obtained from Distillers Co. Ltd. All the above organisms except Pythium acanthiurn were routinely maintained on malt agar + 5% glucose. P. acanthium was maintained on V8 juice agar (20 ml V8 juice, 3 g agar, 80 ml H 2 0 adjusted to pH 6.0 with NaOH). S. cerevisiae, Candida utilis and S. pombe were grown in submerged culture in an orbital incubator at 25°C for 2 days in a medium containing (per 1): 20 g yeast extract (Oxoid), 2 g (NH4)2SO4, 25 g KH2PO 4 and 20 g glucose. P. blakesleeanus was grown for 4 days in an asparagine-containing medium [7]. The other organisms were grown for 1-10 days in liquid complete medium [8]. Fungal extracts were prepared as described by Ansari and Stevens [9]. No proteinase inhibitors were added during the extraction procedures.