Abstract
Glycogen phosphorylase in cell-free extracts of Neurospora crassa is activated 10- to 15-fold by incubation with MgATP2-. When the MgATP2- is removed, the active form (a form) reverts to the inactive form (b form). The inactivation requires Mg2+ and is inhibited by NaF. The results confirm that Neurospora crassa glycogen phosphorylase exists in two interconvertible forms and strongly suggests that the interconversion is catalyzed by a kinase and phosphatase. The a form was partially purified. The enzyme has a molecular weight of 320,000. Uridine diphosphate glucose is a linear competitive inhibitor with respect to glucose-1-phosphate and a linear non-competitive inhibitor with respect to glycogen. Glucose-6-phosphate is a hyperbolic (partial) noncompetitive inhibitor with respect to all substrates in both directions. The b form of the enzyme in crude cell-free extracts is stimulated 2- to 3-fold by 5′-AMP. As the b form is purified, the 5′-AMP activation is diminished. The molecular weight of the partially purified "b" form was also 320,000.
Original language | English (US) |
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Pages (from-to) | 515-527 |
Number of pages | 13 |
Journal | Archives of Biochemistry and Biophysics |
Volume | 161 |
Issue number | 2 |
DOIs | |
State | Published - 1974 |
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Molecular Biology