Dual activity of certain HIT-proteins: A. thaliana Hint4 and C. elegans DcpS act on adenosine 5′-phosphosulfate as hydrolases (forming AMP) and as phosphorylases (forming ADP)

Abstract 

Histidine triad (HIT)-family proteins interact with different mono- and dinucleotides and catalyze their hydrolysis. During a study of the substrate specificity of seven HIT-family proteins, we have shown that each can act as a sulfohydrolase, catalyzing the liberation of AMP from adenosine 5′-phosphosulfate (APS or SO₄-pA). However, in the presence of orthophosphate, Arabidopsis thaliana Hint4 and Caenorhabditis elegans DcpS also behaved as APS phosphorylases, forming ADP. Low pH promoted the phosphorolytic and high pH the hydrolytic activities. These proteins, and in particular Hint4, also catalyzed hydrolysis or phosphorolysis of some other adenylyl-derivatives but at lower rates than those for APS cleavage. A mechanism for these activities is proposed and the possible role of some HIT-proteins in APS metabolism is discussed.

Abbreviations: APS or SO₄-pA, adenosine 5′-phosphosulfate, IPS or SO₄-pI, inosine 5′-phosphosulfate, HIT, histidine triad, HPLC, high performance liquid chromatography, TLC, thin layer chromatography

Keywords: Histidine triad-family protein, Dual catalytic activity, Adenosine 5′-phosphosulfate hydrolysis, Adenosine 5′-phosphosulfate phosphorolysis