V max. activation of pp60c-src tyrosine kinase from neuroblastoma neuro-2A

Publisher Website
Google Scholar
Abstract
A kinetic analysis of the tyrosine-specific protein kinase of pp60c-src from the C1300 mouse neuroblastoma cell line Neuro-2A and pp60c-src expressed in fibroblasts was carried out to determine the nature of the increased specific activity of the neuroblastoma enzyme. In immune-complex kinase assays with ATP-Mn2+ and the tyrosine-containing peptide angiotensin I as phosphoacceptor substrate, pp60c-src from the neuroblastoma cell line was characterized by a maximum velocity (Vmax) that was 7.sbd.15-fold greater than the Vmax of pp60c-src from fibroblasts. The neuroblastoma enzyme exhibited Km values for ATP (16 .+-. 3 .mu.M) and angiotensin I (6.8 .+-. 2.6 mM) that were similar to Km values for ATP (25 .+-. 3 .mu.M) and angiotensin I (6.5 .+-. 1.7 mM) of pp60c-src from fibroblasts. pp60v-src expressed in Rous-sarcoma-virus-transformed cells exhibited an ATP Km value (25 .+-. 4 .mu.M) and an angiotensin I Km value (6.6 .+-. 0.5 mM) that approximated the values determined for pp60c-src in neuroblastoma cells and fibroblasts. These results indicate that the pp60c-src kinase from neuroblastoma cells has a higher turnover number than pp60c-src kinase from fibroblasts, and that the neural form of the enzyme would be expected to exhibit increased catalytic activity at the saturating concentrations of ATP that are found intracellularly.