Protein kinases in chronic lymphocytic leukemia
E Samuel, C Chung, N Scher, B Rosenzweig and R Silber
Experiments were performed to characterize the protein kinase activity in
blood lymphocytes from patients with chronic lymphocytic leukemia (CLL).
Using histone as a substrate, the average specific activity was 397
pmole/min/mg protein. The Km for ATP was 8 muM and for histone 0.3 mg/ml.
The addition of optimal concentrations of cyclic adenosine monophosphate
(cAMP) (1 muM) or cyclic guanosine monophosphate (cGMP) (10muM) resulted in
a 2.2-fold stimulation in activity but had no effect on the Km for ATP or
histone. Most of the properties of the CCL protein kinase were similar to
those of the normal lymphocyte enzyme. These include the pH response,
substrate affinity, as well as rates of phosphorylation and
dephosphorylation. The phosphorylation pattern of endogenous proteins was
determined using intact lymphocytes incubated with 32P and cell-free
homogenates with AT32P. These results indicate that: (1) the
cyclicnucleotide-protein kinase interactions are unimpaired in CLL
lymphocytes; and (2) a sharply defined cyclic nucleotide concentration
response occurs for CLL (as well as normal) lymphocytes, which may explain
the reports of variable inhibitory (and stimulatory) effects on mitogenesis
by these agents.
Volume 55,
Issue 4,
pp. 618-624,
04/01/1980
Copyright © 1980 by The American Society of Hematology
