The enzymic reduction of naphthoquinones by reduced nicotinamide-adenine dinucleotide

Abstract

1. 1. A particulate enzyme system, obtained from cell-free extracts of the H 37 Ra strain of Mycobacterium tubercolosis , catalyzes the reduction of napthoquinones (vitamin K 1 , K 2(20) , K 2(25) , K 2(45) and benzoquinones CoQ 2 , but not CoQ 10 ) by NADH 2 . The reduction of both external quinones and protein-bound K 2(45) has been demonstrated. 2. 2. The reduction of vitamin K 2(45) is inhibited by dicumarol. 3. 3. The particulate enzyme system is solubilized by Triton X-100 and by digitonin treatment. The solubilized enzyme system contains high concentrations of vitamin K 2(45) .