D-alanine—D-alanine ligase - Wikipedia
D-Alanyl-lipoteichoic acid (D-alanyl-LTA) from Lactobacillus casei contains a poly(glycerol phosphate) moiety that is selectively acylated with D-alanine ester residues. To characterize further the mechanism of D-alanine substitution, intermediates were sought that participate in the assembly of this LTA. From the incorporation system utilizing either toluene-treated cells or a combination of membrane fragments and supernatant fraction, a series of membrane-associated D-[14C]alanyl-lipophilic compounds was found. The assay of these compounds depended on their extractability into monophasic chloroform-methanol-water (0.8:3.2:1.0, vol/vol/vol) and subsequent partitioning into chloroform. Four lines of evidence suggested that the D-alanyl-lipophilic compounds are intermediates in the synthesis of D-alanyl-LTA. First, partial degradation of the poly(glycerol phosphate) moiety of D-alanyl-LTA by phosphodiesterase II/phosphatase from Aspergillus niger generated a series of D-alanyl-lipophilic compounds similar to those extracted from the toluene-treated cells during the incorporation of D-alanine. Second, enzymatic degradation of the D-alanyl-lipophilic compounds by the above procedure gave D-alanyl-glycerol, the same degradation product obtained from D-alanyl-LTA. Third, the incorporation of D-alanine into these compounds required the same components as the incorporation of D-alanine into membrane-associated D-alanyl-LTA. Fourth, the phosphate-induced loss of D-[14C]alanine-labeled lipophilic compounds could be correlated with the stimulation of phosphatidylglycerol synthesis in the presence of excess phosphate. We interpreted these experiments to indicate that the D-alanyl-lipophilic compounds are D-alanyl-LTA with short polymer chains and are most likely intermediates in the assembly of the completed polymer, D-alanyl-LTA.
Amino Acid Bio Synthesis | Biosynthesis | Alanine
Tessari P, Vettore M, Millioni R, Puricelli L and Orlando R (2010) Effect of liver cirrhosis on phenylalanine and tyrosine metabolism. Current Opinion in Clinical Nutrition and Metabolic Care 13(1): 81–86.
D-Alanine is a structural component of mycobacterial peptidoglycan. The primary route of D-alanine biosynthesis in eubacteria is the enantiomeric conversion from L-alanine, a reaction catalysed by D-alanine racemase (Alr). Mycobacterium smegmatis alr insertion mutants are not dependent on D-alanine for growth and display a metabolic pattern consistent with an alternative pathway for D-alanine biosynthesis. In this study, we demonstrate that the M. smegmatis alr insertion mutant TAM23 can synthesize D-alanine at lower levels than the parental strain. The insertional inactivation of the alr gene also decreases the intracellular survival of mutant strains within primary human monocyte-derived macrophages. By complementation studies, we confirmed that the impairment of alr gene function is responsible for this reduced survival. Inhibition of superoxide anion and nitric oxide formation in macrophages suppresses the differential survival. In contrast, for bacteria grown in broth, both strains had approximately the same susceptibility to hydrogen peroxide, acidified sodium nitrite, low pH and polymyxin B. In contrast, TAM23 exhibited increased resistance to lysozyme. D-Alanine supplementation considerably increased TAM23 viability in nutritionally deficient media and within macrophages. These results suggest that nutrient deprivation in phagocytic cells combined with killing mediated by reactive intermediates underlies the decreased survival of alr mutants. This knowledge may be valuable in the construction of mycobacterial auxotrophic vaccine candidates.
glutamine and alanine biosynthesis in ..
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Alanine is a precursor in the biosynthesis of fumonisin …
N5-methyl-THF ,as we have just seen, transfers the methylgroup (-CH3), in which the oxidation level of C is that of methanol(-4). N5,N10-methylene-THF carries a methylene group(-CH2-) and the oxidation level is that of formaldehyde (0), while N5-formimino-THFtransfers the formimino group (-CH=NH), in which the oxidation level of the Catom is that of formate. Formyl (-CH=O) and methenyl (-CH=) groups arealso transfered by THF and these both have the C in the oxidation level offormate (+2). The structure of THF is suited for these transfers by virtue ofits N5 and N10 groups as shown in the following chemicalstructure:
Impairment of D-Alanine biosynthesis in …
Alanine synthesisis is a bit of a mystery. Several reactions have been identified, but it has been impossible to generate an alanine and therefore positively identify a required pathway. There are several pathways and the most likely is formation of alanine by transamination from glutamate onto pyruvate. A transamination using valine instead of glutamate is also possible.