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Properties and kinetics of glucan phosphorylase of the amylose‐forming yeast Cryptococcus laurentii
Author(s) -
Foda M. S.,
Phaff H. J.
Publication year - 1978
Publication title -
zeitschrift für allgemeine mikrobiologie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0044-2208
DOI - 10.1002/jobm.19780180203
Subject(s) - amylose , glucan , glycogen phosphorylase , chemistry , biochemistry , enzyme , starch , yeast , chromatography , nuclear chemistry
Cell extracts of Cryptococcus laurentii , a yeast which synthesizes amylose when grown at low pH, contained an α‐glucan phosphorylase (α‐1·4)‐glucan: orthophosphate glucosyl transferase (EC 2.4.1.1). The enzyme, which is very labile, showed greatest stability at pH 8.0 in the presence of 0.1 m β‐glycerophosphate and 0.1 m sodium fluoride. Based upon visible colour development with iodine a cell homogenate, centrifuged at 32,000 g to remove cell debris, synthesized starch‐like polymers upon incubation with glucose‐1‐phosphate in a pH range of 5.6‐6.1. Based upon incorporation of labelled glucose from glucose‐1‐phosphate the pH of maximum activity was 5.9‐6.2. The enzyme was partially purified by glycogen complexing, precipitation, and adsorption on hydroxylapatite followed by elution. The purified enzyme has a K m for glucose‐1‐phosphate of 1.6 × 10 −2 m. Mutants impaired in their ability to synthesize amylose contained approximately one fourth of the phosphorylase activity as compared to the wild type. The possible role of the glucan phosphorylase in amylose biosynthesis is discussed.