Biosynthesis of Menaquinone (Vitamin K ₂ ) and Ubiquinone (Coenzyme Q)

Abstract

Escherichia coli and Salmonella contain the naphthoquinones menaquinone (MK; vitamin K 2 ) and demethylmenaquinone and the benzoquinone ubiquinone (coenzyme Q; Q). Both quinones are derived from the shikimate pathway, which has been called a "metabolic tree with many branches." There are two different pathways for the biosynthesis of the naphthoquinones. The vast majority of prokaryotes, including E. coli and Salmonella , and the plants use the o -succinylbenzoate pathway, while a minority uses the futalosine pathway. The quinone nucleus of Q is derived directly from chorismate, while that of MK is derived from chorismate via isochorismate. The prenyl side chains of both quinones are from isopentenyl diphosphate formed by the 2- C -methyl-D-erythritol 4-phosphate (non-mevalonate) pathway and the methyl groups are from S -adenosylmethionine. In addition, MK biosynthesis requires 2-ketoglutarate and cofactors ATP, coenzyme A, and thiamine pyrophosphate. Despite the fact that both quinones originate from the shikimate pathway, there are important differences in their biosyntheses. The prenyl side chain in MK biosynthesis is introduced at the penultimate step, accompanied by decarboxylation, whereas in Q biosynthesis it is introduced at the second step, with retention of the carboxyl group. In MK biosynthesis, all the reactions of the pathway up to prenylation are carried out by soluble enzymes, whereas all the enzymes involved in Q biosynthesis except the first are membrane bound. In MK biosynthesis, the last step is a C -methylation; in Q biosynthesis, the last step is an O -methylation. In Q biosynthesis a second C -methylation and O -methylation take place in the middle part of the pathway. Despite the fact that Q and MK biosyntheses diverge at chorismate, the C -methylations in both pathways are carried out by the same methyltransferase.

Pre- and post-weaning diet alters the faecal metagenome in the cat with differences in vitamin and carbohydrate metabolism gene abundances

“…For example, 1 g taurine per kg DM is required in kibbled diets whereas canned diets require 2 g taurine per kg DM diet50. Additionally, the relationship between taurine and Maillard reaction products and intestinal microbiota has been of interest for the cat since work published in 1996 showed that Maillard reaction products induced taurine depletion in the cat and that this could be reversed with antibiotics65.…”

Prenyltransferases as key enzymes in primary and secondary metabolism

“…Members of this enzyme group are involved in the biosynthesis of both primary metabolites such as ubiquinones and menaquinones (Boronat and Rodriguez-Concepcion 2015;Meganathan and Kwon 2009) and secondary metabolites like microbial and plant natural products (Holm et al 2014;Wang et al 2014;Yazaki et al 2009;Zeyhle et al 2014a, b).…”

Mechanism of MenE Inhibition by Acyl-Adenylate Analogues and Discovery of Novel Antibacterial Agents

“…This pathway consists of at least nine enzymes that catalyze the formation of menaquinone from chorismate [12, 13, 16] . The fifth enzyme, MenE, is an acyl-CoA ligase which ligates CoA to OSB via an OSB-AMP intermediate.…”