A mutant of barley lacking NADH-hydroxypyruvate reductase

A mutant of barley, LaPr 88/29, deficient in peroxisomal NADH-hydroxypyruvate reductase (HPR) activity has been identified. Compared to the wild type the activities of NADH-HPR and NADPH-HPR were severely reduced but the mutant was still capable of fixing CO2 at rates equivalent to 75% of that of the wild type in air. Although lacking an enzyme in the main photorespiratory pathway, there appeared to be little disruption to photorespiratory metabolism as ammonia release, CO2 efflux and 14CO2 release from L-[U-14C] serine were similar in both mutant and wild type. LaPr 88/29 has been used to show that NADH-glyoxylate reductase (GR) and NADH-HPR are probably not catalyzed by the same enzyme in barley and that over 80% of the NADPH-HPR activity is due to the NADH-HPR enzyme. Immunological studies, using antibodies raised against spinach HPR, have shown that the NADH-dependent enzyme protein is absent in LaPr 88/29 but there appears to be enhanced synthesis of the NADPH-dependent enzyme protein