Abstract
Until now, no enzymes were described that hydrolyze cyanophycin granular protein (CGP) from a species of the genus Streptomyces . An isolate able to hydrolyze CGP was identi fied as Streptomyces pratensis strain YSM. The CGPase from S. pratensis strain YSM had an optimum activity at 42 ?C and pH 8.5, and was able to degrade CGP at a rate of 12 ? 0.3 ?g/mL min. Additionally, this CGPase hydrolyzes water-soluble CGP signi ficantly faster than water -insoluble CGP. The molecular mass of CGPase subunits from S. pratensis strain YSM as determined by SDS-PAGE was about 43 kDa, and the enzyme was entirely inhibited by serine-protease inhibitors. The CGPase coding gene ( cphE Strept. ) was ampli fied from genomic DNA using primers designed form consensus sequence of putative CGPase sequences. The cphE Strept. was 1427 bp encoding a CGPase of 420 amino acids that showed about 44% and 22% similarities to CGPase from Pseudomonas anguilliseptica BI and Synechocystis sp. PCC 6803, re- spectively. The catalytic triad and serine-protease residues (GXSXG) were identi fied in the CphE Strept. sequence. Dipeptides and tetrapeptides were identi fied as hydrolysis products. Biotechnological exploitation of S. pratensis strain YSM for CGPase production might have an advantage due to the reduction of separation costs and its ability to degrade CGP in phosphate bu ffer saline using actively growing or resting cells.