title: A comparative kinetic analysis of six substrates widely used for the detection and quantitation of phosphodiesterase I.
abstract: Six of the substrates currently used for the detection and quantitation of phosphodiesterase I (PDE I) were examined. Michaelis-Menten kinetic analysis of the hydrolysis of each of these by venom and bovine intestinal PDE I was performed to allow a comparison of the sensitivity of detection for each substrate. The results confirm that phenolic esters of phenylphosphonate are hydrolyzed 2- to 4-fold more rapidly than are the same esters of thymidine 5'-phosphate when both are present in saturating concentrations. The identification of the bovine intestinal enzyme as a PDE I is verified by its extensive similarity to the paradigmatical PDE I from rattlesnake venom. A new definition for PDE I activity is proposed which takes into account its ability to hydrolyze several types of substrates.
mesh_terms: D000818:Animals; D002417:Cattle; D006868:Hydrolysis; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D009596:Nitrophenols / Q000378:metabolism; D043264:Phosphodiesterase I; D010727:Phosphoric Diester Hydrolases / Q000032:analysis / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D009596:Nitrophenols; D006923:Hymecromone; C002887:bis(4-nitrophenyl)phosphate; C033127:4-methylumbelliferyl thymidine 5'-phosphate; C037946:4-methylumbelliferyl phenylphosphonate; D010727:Phosphoric Diester Hydrolases; D043264:Phosphodiesterase I