Amino acids intracellular pool

Experiments have been described94 in which small amounts of tracer have been incorporated into juvenile hormones from amino-acid precursors under conditions where the intracellular pool size of these precursors may be determined by routine methods, and an assay procedure has been developed95 by which the esterification of farnesenic acid with the methyl group from methionine, and the 10,11-epoxidation of the resultant ester to yield JH-III, can be measured in corpora allata of the adult female Schistocerca gregaria. 

Different species of macroalgae would be expected to have different N release rates. For example, some macroalgae are known to have large intracellular inorganic N storage pools (e.g., McGlathery et ah, 1996). Release of NH4", as measured with isotope dilution, was observed in Ulva fenestrata (0.08-11.27 pmol N g h ) and Gracilaria pacifica (0.12-0.77 pmol N g h ) when NH4+ was added to the medium. However, no net NH4+ release, over uptake, was observed. Small pulses of free amino acids were released and then rapidly reincorporated (Naldi and Wheeler, 2002), but no protein release was detectable. 

Although cephalosporin C is divisable into a-aminoadipic acid, cysteine, and valine, the actual mechanism whereby Cephalosporium sp. incorporates the three amino acids into cephalosporin C has not been established, Arnstein and Morris isolated 8 (a-aminoadipyl) cysteinyl valine from mycelia of Penicillium chrysogenum and suggested that the tripeptide is a precursor in all penicillin biosynthesis.. This same tripeptide also appears to be found in the intracellular pool of Cephalosporium sp.- The final postulated step in the biosynthesis of penicillin is an acyl transfer reaction, or the production of 6-aminopeni-cillanic acid if precursor is not added. Cephalosporium sp. apparently do not produce sidechain amidases or acyl transferases, and no 7-ACA has been reported found in the fermentation. Thus, to obtain clinically useful antibiotics, chemical manipulation of cephalosporin C is necessary. Synthesis of many 7-acyl derivatives was possible once a practical cleavage reaction made available large amounts of 7-ACA from cephalosporin C. of these derivatives, sodium cephalothin was the first... 

FI 4. Furst, P., Alvesstrand, A., and Bergstrom, J., Effect of nutrition and catabolic stress in intracellular amino acid pools in uremia. Am. J. Clin. Nutr. 33, 1387-1395 (1980). 

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