Peroxisomes hydroxypyruvate reductase

Chloroplasts contain a specific glyoxylate reductase active with NADPH as coenzyme an enzyme in peroxisomes that catalyzes glyoxylate reduction by NADH is not specific and probably functions mainly as hydroxypyruvate reductase (Tolbert et al., 1970) (this is discussed in Section II,A,2). These enzymes could conceivably be involved in the oxidation of glycolate to provide glyoxylate for synthesis of glycine. 

A number of enzymic steps of the photorespiratory pathway, including the reduction of hydroxypyruvate to glycerate, are located in the peroxisomes (Fig. 2). For this reaction occurring at high rates the NADH has to be provided from outside the peroxisomes. Peroxisomal enzymes, such as hydroxypyruvate reductase, show latency (13). Recent experiments carried out in our laboratory have shown that this latency is not due to an impermeability of the peroxisomal membrane. It appears that the peroxisomal proteins form a dense matrix which is not affected by... 

For Method see (10,13). By using hydroxypyruvate reductase as marker enzyme, the activity obtained with the isolated peroxisomes was related to the chlorophyll content in a spinach leaf. 

Enzyme activities of nonreversible NADP-glyceraldehyde 3-phosphate dehydrogenase and NADP-isocitrate dehydrogenase as marker for the cytosol, hydroxypyruvate reductase for peroxisomes and cytochrom c reductase for mitochondria were 0.3 to 2% compared to those of the total leaf extract. 

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