Purification and Properties of Malate Dehydrogenase from the Thermoacidophilic ArchaebacteriumThermoplasma addophilum

Publisher Website
Google Scholar
Abstract
Malate dehydrogenase from the thermoacidophilic archaebacterium Thermoplasma acidophilum is purified 50-fold to electrophoretic homogeneity. The purified enzyme crystallizes readily. Native malate dehydrogenase shows a relative molecular mass of 144,000. It is a tetramer of identical subunits with a relative molecular mass of 36,600. Malate dehydrogenase from Thermoplasma uses both NADH and NADPH as coenzyme to reduce oxaloacetate. The enzyme shows A-side (pro-R) stereospecificity for both coenzymes. The pH optimum for the reduction of oxaloacetate in the presence of NADH is found to be at pH 8.1. At pH 7.4 the Km value for oxaloacetate is found to be 5.6 .mu.M while for NADH a value of 11.7 .mu.M is found. The homogeneous enzyme shows a turnover number of kcat = 108 s-1.