A cyanophycin synthetase from Thermosynechococcus elongatus BP-1 catalyzes primer-independent cyanophycin synthesis

Toshinobu Arai, Kuniki Kino

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Cyanophycin synthesis is catalyzed by cyanophycin synthetase (CphA). It was believed that CphA requires l-aspartic acid (Asp), l-arginine (Arg), ATP, Mg2+, and a primer (low-molecular mass cyanophycin) for cyanophycin synthesis and catalyzes the elongation of a low-molecular mass cyanophycin. Despite extensive studies of cyanophycin, the mechanism of primer supply is still unclear, and already-known CphAs were primer-dependent enzymes. In the present study, we found that recombinant CphA from Thermosynechococcus elongatus BP-1 (Tlr2170 protein) catalyzed in vitro cyanophycin synthesis in the absence of a primer. The Tlr2170 protein showed strict substrate specificity toward Asp and Arg. The optimum pH was 9.0, and Mg2+ or Mn2+ was essential for cyanophycin synthesis. KCl enhanced the cyanophycin synthesis activity of the Tlr2170 protein; in contrast, dithiothreitol did not. The Tlr2170 protein appeared to be a 400±9 kDa homo-tetramer. The Tlr2170 protein showed thermal stability and retained its 80% activity after a 60-min incubation at 50°C. In addition, we examined cyanophycin synthesis at 30°C, 40°C, 50°C, and 60°C. SDS-PAGE analysis showed that the molecular mass of cyanophycin increased with increased reaction temperature.

Original languageEnglish
Pages (from-to)69-78
Number of pages10
JournalApplied Microbiology and Biotechnology
Volume81
Issue number1
DOIs
Publication statusPublished - 2008 Nov 1

Keywords

  • Cyanophycin synthetase
  • Primer independent
  • Thermosynechococcus elongatus BP-1

ASJC Scopus subject areas

  • Biotechnology
  • Applied Microbiology and Biotechnology

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