Effect of cystathionine and cystathionine metabolites on the phosphorylation of tyrosine residues in human neutrophils.

The effect of cystathionine and cystathionine metabolites found in the urine of patients with cystathioninuria on the phosphorylation of tyrosine residues was studied with human peripheral blood polymorphonuclear leukocytes. Among the cystathionine metabolites, cystathionine ketimine markedly increased phosphorylation of a 45 kDa protein with time and the phosphorylation depended on the concentration of cystathionine ketimine, while cystathionine and the reduced form of cystathionine ketimine (cyclothionine) did not increase the phosphorylation of the 45 kDa protein. The phosphorylation of the 45 kDa protein induced by cystathionine ketimine was inhibited by genistein and herbimycin A, inhibitors of tyrosine kinase, but was not inhibited by 1-(5-isoquinolinesulfonyl)-2-methylpiperazine and staurosporine, inhibitors of protein kinase C.