Identification of hydroxypyruvate reductase from parsley by peptide sequence comparison after a two-step purification

Hydroxypyruvate reductase (HPR), a plant leaf peroxisomal enzyme involved in the glycolate pathway, has been purified in two steps from a crude extract of parsley leaves during the purification of an unrelated ATP-dependent enzyme. HPR, a homogenous side-fraction arising from this purification procedure, was identified after sequencing of three internal peptides which showed near 100% homology with the amino acid sequence deduced from the cDNA encoding the NADH-dependent HPR from cucumber. This is an example of the identification of the activity of an unknown protein through direct sequence work. Some of the parsley HPR physicochemical and kinetic properties are similar to those of the cucumber enzyme.