The disclosure provides methods and compositions for determining the kinase activity profile of a biological sample, e.g., that contains multiple kinases.

The technical problem to be solved by the present invention is to provide a method for producing glutathione and a precursor thereof, -glutamylcysteine, at a high yield. As a means for solving the problem, the method for producing glutathione according to the present invention includes step A of reacting L-cysteine and L-glutamic acid under a low-oxygen atmosphere to produce -glutamylcysteine and step B of reacting -glutamylcysteine and glycine under a low-oxygen atmosphere to produce glutathione.