Contribution of cysteamine dioxygenase to taurine biosynthesis in the oyster Crassostrea gigas

Abstract

The Pacific oyster Crassostrea gigas is well-known for its exceptionally high taurine content, but the mechanisms underlying taurine biosynthesis remain largely unexplored. Thecysteamine (AET) pathway is one of the primary metabolic routes involved in taurine biosynthesis, and its role in mollusk taurine synthesis has garnered increasing recognition. In the present study, a cysteamine dioxygenase (ADO) homolog CgADO, the central enzyme of the AET pathway, was identified in C. gigas, which contained a typical PCO_ADO domain. The transcripts of CgADO were constitutively expressed in examined oyster tissues, with the highest level detected in the adductor muscle while the lowest in the hepatopancreas. The recombinant CgADO protein, expressed in Escherichia coli, was capable of converting cysteamine to hypotaurine. Overexpression of CgADO in HEK293T cells increased the production of taurine by 20.31-fold, compared to cells transfected with the empty vector. Inhibition of endogenous CgADO expression using RNA interference resulted in a 49% reduction in its mRNA expression and an 8% decline in taurine content in the adductor muscle of oysters. These results indicated that CgADO functioned as a cysteamine dioxygenase and played a certain role in taurine biosynthesis in C. gigas.

Keywords: Crassostrea gigas; Cysteamine dioxygenase; Cysteamine pathway; Taurine biosynthesis.