Homogeneous preparations of D-glyceraldehydc.3-phosphate dehydrogenase purified from rabbit muscle were found to contain 0,2-0,7 moles of covalently bound phosphate per mole of the enzyme. With the use of anti-phospholyrosine antibodies, evidence was obtained that the enzyme is phosphorylated at tyrosine residues.o-Glyeeraldehyde-3-phosphate dehydrogenase; Endogenous phosphate; Phosphotyrosine; Antibody to phosphotyrosine

A biologically active synthetic peptide, 2438, representing the 124–138 amino acid sequence of the human interferon α‐2 (IFN α‐2) molecule, which is known to possess IFN‐like antiproliferative activity, specifically binds to human blood leukocytes. Scatchard plots reveal two different K fd values, for the ‘low’ and ‘high’ affinity binding. The interaction of the 125I‐labelled peptide 2438 with the cells is not impaired by human IFN α‐2 or cholera toxin.

Tyrosinc phosphorylation in human blood lymphocytes was studied as a function of stimulation with concanavalin A (ConA) and treatmem of the cells with interferon a? (IFNa2) and/or an IFN-derived C-terminal synthetic pcptidc 2438 (amino acid residues 124-138). Both IFNa? and the prptide 2438 decreased the level of protein tyrosinc phosphorylation in the ConA-stimulated cells. In unstimulated cells, IFNaI) increased, and the peptide 2438 decreased the level of the tyrosinc phosphorylation. A possible correlation of these effects with stimulation of cell proliferation is discussed.