Apyrase 2642217 171304131 2007-11-13T22:38:42Z Alaibot 1324179 Robot: sorting stub (based on existing categorisation) '''Apyrase''' is a [[calcium]]-activated plasma membrane-bound [[enzyme]] (magnesium can also activate it) ({{EC number|3.6.1.5}}) that [[catalyst|catalyses]] the [[hydrolysis]] of [[Adenosine triphosphate|ATP]] to yield [[Adenosine monophosphate|AMP]] and [[inorganic phosphate]]. Two isoenzymes are found in commercial preparations from ''S. tuberosum''. One with a higher ratio of substrate selectivity for ATP:ADP (approx 10) and another with no selectivity (ratio 1). It can also act on [[Adenosine diphosphate|ADP]] and other [[nucleoside]] [[triphosphates]] and [[diphosphates]] with the general reaction being NTP -> NDP + Pi -> NMP + 2Pi. It is the [[enzyme]] released by female [[mosquito]]es to prevent [[blood clot]]s when they suck blood. The activity of apyrase at pH 7.5 in a Tris Buffer is approximately 80% of the activity at pH 6.5. ==External links== * {{MeshName|Apyrase}} [[Category:EC 3.6.1]] {{hydrolase-stub}} {{Acid anhydride hydrolases}}