Polyamines alter the substrate preference of nuclear protein kinase NII.
When investigating the effects of polyamines on substrate specificity of adenosine cyclic 3', 5'-monophosphate (cAMP) independent nuclear protein kinase NII, we found that the substrate preference of NII was drastically altered in the presence of polyamines. When casein was used as a substrate, spermine stimulated the enzyme activity 7.3-fold at 2 mM, and a 6.5-fold stimulation was observed with 6 mM spermidine. Putrescine was also slightly effective at higher concentrations. With phosvitin as the substrate, however, 2 mM spermine and 4 mM spermidine strongly inhibited the activity by 93% and 80%, respectively, while putrescine showed a weak stimulatory effect. Steady-state kinetics and binding studies suggested that both stimulatory and inhibitory effects of polyamines on NII enzyme activity are probably due to substrate protein-polyamine interactions. The circular dichroism spectrum of phosvitin was apparently altered by spermine, whereas no significant change was observed with casein.
D000818:Animals; D002364:Caseins / Q000378:metabolism; D002467:Cell Nucleus / Q000201:enzymology; D002942:Circular Dichroism; D008099:Liver / Q000201:enzymology; D008297:Male; D010774:Phosvitin / Q000378:metabolism; D011073:Polyamines / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D013379:Substrate Specificity
D002364:Caseins; D011073:Polyamines; D010774:Phosvitin; D011494:Protein Kinases