Tyrosine protein kinase (TPK) co-isolated with subcellular components derived from human colonic epithelium. The highest TPK activity, measured in the Triton X-100-insoluble cytoskeletal pellet, was directly related to the degree of malignancy of colonic tissue. TPK activity was assayed by measuring the incorporation of [γ-32P] from [γ32]ATP into the synthetic polymer [Glu80Tyr20](n) substrate. Lineweaver-Burk plots yielded an apparent Km of 167 μg/ml for [Glu80Tyr20](n) and of 19μM for ATP: V(max) for the phosphate donor was 0.9 nmol/min/mg protein. TPK activity was markedly stimulated by the metal ions Mg2+ and Mn2+ and significantly suppressed by tyrphostins, potent specific TPK inhibitors, shown to interfere with TPK-dependent growth processes. This is the first report to present evidence for TPK activity associated with cytoskeleton-enriched subcellular preparations harvested from human colonic epithelium.
|Original language||American English|
|Number of pages||7|
|State||Published - 1990|
- tyrosine protein kinase