Sequence and Regulation of Vitamin K Biosynthesis Genes

Meganathan, Rangaswamy

Abstract

The principal aim of this investigation is to gain insight into the regulation of bacterial vitamin K biosynthesis by the molecular examination and dissection of the structure and organization of vitamin K biosynthetic genes. Vitamin K is an important fat soluble vitamin which plays a significant role in human and animal health. Its deficiency leads to several significant clinical pathologies such as hypoprothrombinemia. In healthy individuals the bulk of the vitamin K requirement is met by bacterial biosynthesis of intestinal flora. The pathway for the vitamin k napthoquinone nucleus is reasonably understood, and the genes involved in the synthesis of the various enzymes have been mapped and cloned. The synthesis of the vitamin is dependent upon the aromatic amino acid pathway and utilizes isochorismate and 2-ketoglutarate as initial reactants. The identified intermediates are 2-succinyl-6-hydroxy-2,4- cyclohexadiene-1-carboxylate (SHCHC), o-succinylbenzoate (OSB) ester of OSB (OSB-CoA), 1,4-dihydroxy-2-naphthoate (DHNA) and desmethylmenaquinone (DMK). The menA gene is located at 88 min and the menBCDE gene cluster at 48.5 min of E. coli linkage map. The men cluster has been cloned into pBR322 and the DNA sequence of menD determined. This investigation will determine the sequence of the remaining men cluster genes and initiate studies of the regulation of these genes using lacZ fusions.