The effect of heparin on the activity of Trichosporon cutaneum casein kinase I

Abstract

Casein kinase I from Trichosporon cutaneum ribosome-free extracts was purified. Its molecular mass was calculated for 33 kDa. It was shown that casein, phosvitin and Trichosporon cutaneum ribosomal protein of 15 kDa were preferable substrates for the enzyme. It was found that heparin can stimulate or inhibit CKI activity depending on the substrate used. Stimulation of casein and inhibition of phosvitin phosphorylation was observed. In addition it was shown that ribosomal proteins of 19 kDa and 38 kDa were phosphorylated by CKI only in the presence of heparin.

Protein kinases CKI and CKII are implicated in modification of ribosomal proteins of the yeast Trichosporon cutaneum.

“…Our earlier studies (Cytryñska et al, 1995;Wojda et al, 1997;1999) and the results presented in this paper indicate that in T. cutaneum, similarly to other yeast species, the complex of acidic ribosomal proteins P1/P2-P0 is modified by CKII. Additionaly, in T. cutaneum ribosomes, but not in other yeast species, a protein of 19 kDa is also phosphorylated by CKII.…”

“…We also showed that heparin changed the substrate specificity of CKI. A ribosomal protein of about 20 kDa was phosphorylated only in the presence of this polyanion (Wojda et al, 1997;1999). In this paper we show that in the presence of heparin at 5 mg/ml (but not at 40 mg/ml) a significant increase in the phosphorylation level of the 40 kDa protein was visible.…”

“…For a long time heparin had been considered a potent inhibitor of CKII, but not CKI activity. We showed before that the activity of CKI of T. cutaneum can be inhibited by heparin when phosvitin, but not casein, was used as the phosphorylation substrate (Wojda, 1997). We also showed that heparin changed the substrate specificity of CKI.…”