The actívities of glycine oxidase (GO) and serine dehydratase (SD) were revealed in green leaves of wheat and maize. The enzymes were extracted by ammonium sulfáte fractionation. GO localized in chloroplast and cytosolic fraction was most active at pH 8.0. Its activity was 1.5-2.0 times higher in wheat than in maize and it declined with leaf aging. The enzyme converts glycine into glycollate and ammonium ion being flavine dependent and generating H2O2. We propose that it is an L-amino-acid oxidase (EC 1.4.3.2) with a higher specificity to glycine. The activity of SD (EC 4.2.1.13) localized in chloroplasts was maximum at pH 7.0-7.2, it was also higher in wheat than in maize. Pyruvate was determined as a product of enzymatic conversion of L-serine. SD and GO actívities were not revealed in etíolated leaves.