In Vitro Functional Study of Rice Adenosine 5’-Phosphosulfate Kinase

Sulfate can be activated by ATP sulfurylase and adenosine 5’-phosphosulfate kinase (APSK) in vivo. Recent studies suggested that APSK in Arabidopsis thaliana regulated the partition between APS reduction and phosphorylation and its activity can be modulated by cellular redox status. In order to study regulation of APSK in rice (OsAPSK), OsAPSK1 gene was cloned and its activity was analyzed. OsAPSK1 C36 and C69 were found to be the conserved counterparts of C86 and C119, which involved in disulfide formation in AtAPSK. C36A/C69A OsAPSK1 double mutation was made by site directed mutagenesis. OsAPSK1 and its mutant were prokaryotically over-expressed and purified, and then assayed for APS phosphorylation activity. OsAPSK1 activity was depressed by oxidized glutathione, while the activity of its mutant was not. Further studies in the case that oxidative stress will fluctuate in vivo 3’-phosphoadenosine-5’-phosphosulfate content, and all APSK isoenzymes have similar regulation patterns are necessary to be performed.