Glycogen phosphorylase (α-1,4-glucan: orthophosphate glucosyltransferase, EC 18.104.22.168) from rat placenta has been shown to exist in AMP-dependent and -independent forms that are designated phosphorylase b and a, respectively. Phosphorylase b exhibits a Ka of 1.5·10-4 M for AMP and is stimulated by 0.7 M Na2SO4 in the presence or absence of the nucleotide; in contrast, phosphorylase a is inhibited by Na2SO4. Placental extracts contain a phosphorylase kinase, a phosphorylase phosphatase and a cyclic AMP-dependent protein kinase which are presumed to be associated with the control of glycogenolysis in this tissue.
ASJC Scopus subject areas
- Molecular Biology