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The YggS/PLPBP protein (also called COG0325 or PLPHP) is a conserved pyridoxal 5 '-phosphate (PLP) -binding protein present in all 3 domains of life. Recent studies have demonstrated that disruption or mutation of this protein has multifaceted effects in various organisms, including vitamin B6 -dependent epilepsy in humans. In Escherichia coli, disruption of this protein--encoded by yggS--perturbs Thr-Ile/Val metabolism, one-carbon metabolism, coenzyme A synthesis, and vitamin B6 homeostasis. This protein is critical for maintaining low levels of pyridoxine 5 '-phosphate (PNP) in various organisms. In the yggS -deficient E. coli strain, inhibition of PLP-dependent enzymes, such as the glycine cleavage system by PNP, is the root cause of metabolic perturbation. Our data suggest that the YggS/PLPBP protein may be involved in the balancing of B6 vitamers by mediating efficient turnover of protein-bound B6 vitamers. This paper reviews recent findings on the function of the YggS/PLPBP protein. [ABSTRACT FROM AUTHOR]

Nudix hydrolases typically catalyze the hydrolysis of nucleoside diphosphate linked to moiety X and yield nucleoside monophosphate and X-phosphate, while some of them hydrolyze a terminal diphosphate group of non-nucleosidic compounds and convert it into a phosphate group. Although the number of Nudix hydrolases is usually limited in archaea comparing with those in bacteria and eukaryotes, the physiological functions of most archaeal Nudix hydrolases remain unknown. In this study, a Nudix hydrolase family protein, MM_2582, from the methanogenic archaeon Methanosarcina mazei was recombinantly expressed in Escherichia coli, purified, and characterized. This recombinant protein shows higher hydrolase activity toward isopentenyl diphosphate and short-chain prenyl diphosphates than that toward nucleosidic compounds. Kinetic studies demonstrated that the archaeal enzyme prefers isopentenyl diphosphate and dimethylallyl diphosphate, which suggests its role in the biosynthesis of prenylated flavin mononucleotide, a recently discovered coenzyme that is required, for example, in the archaea-specific modified mevalonate pathway. [ABSTRACT FROM AUTHOR]

(E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMBPP) is an intermediate of the methylerythritol phosphate pathway. Utilization of HMBPP by lycopene elongase from Corynebacterium glutamicum, which is a UbiA-family prenyltransferase responsible for C50 carotenoid biosynthesis, was investigated using an Escherichia coli strain that contained the exogenous mevalonate pathway as well as the carotenoid biosynthetic pathway. Inhibition of the endogenous methylerythritol phosphate pathway resulted in loss of the production of C50 carotenoid flavuxanthin, while C40 lycopene formation was retained. Overexpression of E. coli ispH gene, which encodes HMBPP reductase, also decreased the production of flavuxanthin in E. coli cells. These results indicate the preference of lycopene elongase for HMBPP instead of the previously proposed substrate, dimethylallyl diphosphate. Furthermore, several (all-E)-prenyl diphosphate synthases, which are classified in a distinct family of prenyltransferase, were demonstrated to accept HMBPP, which implies that the compound is more widely used as a prenyl donor substrate than was previously expected. [ABSTRACT FROM AUTHOR]