Assays for methionine γ-lyase and S-adenosyl-L-homocysteine hydrolase based on enzymatic formation of CdS quantum dots in situ.

S-Adenosyl-L-homocysteine hydrolase (AHCY) hydrolyzes its substrate S-adenosyl-L-homocysteine (AdoHcy) to L-homocysteine (Hcy). Methionine γ-lyase (MGL) catalyzes the decomposition of Hcy to hydrogen sulfide which forms fluorescent CdS nanoparticles in the presence of Cd(NO(3))(2). On the basis of these enzymatic reactions, two new simple and robust fluorogenic enzymatic assays for MGL and AHCY were developed and applied to detection of AHCY inhibitors.