Compartmentation studies on spinach leaf peroxisomes

The synthesis of glycerate by isolated intact spinach (Spinacia oleracea L.) leaf peroxisomes upon the addition of glycolate, serine, and glutamate, with either NADH or malate as reductant, has been measured. Measurement of the concentration dependence of NADH-and malate-dependent glycerate synthesis, and the exclusion of various artefacts, clearly demonstrate that under in vivo conditions the transfer of reducing equivalents into the peroxisomes required for the reduction of hydroxypyruvate to glycerate, occurs exclusively via a malate shuttle. The results indicate that a direct uptake of NADH into the peroxisomes does not occur under invivo conditions to any appreciable extent. As these results have been observed with intact as well as with osmotically shocked peroxisomes, it is concluded that the specificity of redox transfer into the peroxisomes is not due to a selectivity of the peroxisomal boundary membrane, but to a multi-enzyme structure of the peroxisomal matrix.Abbreviations GDH glycerophosphate dehydrogenase - GOT glutamate oxaloacetate transaminase - HPR hydroxy-pyruvate reductase - MDH malate dehydrogenaseThe authors are indebted to Mr. Bernd Raufeisen for the art work. This work was supported by the Deutsche Forschungsgemeinschaft.