UDP-GNAc

The toxic effects produced by ammonium are (i) enzymatic inhibition (in glycolysis, TCA cycle, glutaminolysis, and PPC) (ii) perturbation of the transcellular ionic gradient (iii) intracellular pH modification (iv) increase of UDP-GNAc synthesis, with concomitant glycolysis modification and affecting the quality of the recombinant protein and (v) increase in the alanine secretion. 

UDP-GNAc-laotyl-L-ala (Park s compound 2) UDP-GNAc-lactyl-L-ala-D-glu UDP-GNAc-laotyl-L-ala-D-glu-L-lys UDP-GNAc-laotyl-L-ala-n-glu-L-lys-D-ala-D-ala (Park s compound 3)... 

UDP-GNAc -b UDP-GA GNAc-GA-UDP + UDP GNAc-GA-UDP -t- GNAc-GA-UDP GNAc-GA-GNAc-GA-UDP + UDP... 

The mechanism of synthesis of hyaluronic acid in mammalian tissues appears to resemble that present in bacteria. The synthesis of hyaluronic acid in tissue culture has been widely studied (GIO, H7), and labeled hyaluronic acid is synthesized in vitro from uniformly labeled D-glucose by explants of human synovial tissue (Yl). An enzyme system has recently been found in mesodermal tissues which catalyzes the synthesis of hyaluronic acid directly from UDP-GNAc and UDP-GA (A5). 

The nucleotide UDP-GNAc-lactyl-L-Ala-D-Glu-L-Lys accumulates in Staph, aureus treated with D-cycloserine. This accumulation is inhibited competitively by D-alanine, but not by its L-isomer. It has thus been suggested that the antibacterial activity of D-cycloserine (XXVIII) depends on its structural similarity to D-alanine, which enables it to inhibit the incorporation of the latter into the muramic acid-peptide of the cell wall. 

Park and Johnson found that three uridine nucleotides accumulated in Staph, aureus treated with penicillinii . The major nucleotide (LVIII) was later shown to consist of uridine 5 -pyrophosphate (UDP) linked to a new N-acetylamino sugar that is linked in turn to a peptide. The new amino sugar occurs in the cell walls of a number of bacteria and has been named muramic acid. It is an ether of D-glucosamine and lactic acid (GNAc-lactic)... 

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