Experiments in marine biochemistry. Homarine metabolism in Penaeus duorarum.
A fractionation procedure has been developed which permits the isolation of 1 to 2 mg of homarine from a single shrimp. This procedure was used to show that homarine is endogenously synthesized by Penaeus duorarum in the free unbound form, and to study the metabolic precursors involved. Injected DL-[14C]tryptophan was not converted to [14C]homarine. However, [6-14C]quinolinic acid, a known catabolite of tryptophan, is an effective precursor. [2-14C]Acetate and [U-14C]glycerol are effectively converted to [14C]homarine while [14C]bicarbonate is poorly utilized. The injection of L-[U-14C]aspartate resulted in labeled homarine, but the quantity converted was less than expected. Since [14C]glycerol is an effective precursor there is a possibility that quinolinic acid may be formed in P. duorarum by a condensation similar to that of glyceraldehyde 3-phosphate with aspartic acid or a closely related metabolite. It is suggested that decarboxylation of quinolinic acid gives rise to picolinic acid which is methylated to yield homarine. L-[methyl-14C]Methionine efficiently provides the N-methyl carbon presumably via S-adenosylmethionine.
D000085:Acetates / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D005990:Glycerol / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D033561:Penaeidae / Q000378:metabolism*; D010848:Picolinic Acids / Q000302:isolation & purification / Q000378:metabolism*; D011805:Quinolinic Acids / Q000378:metabolism; D012623:Seawater; D014364:Tryptophan / Q000378:metabolism
D000085:Acetates; D001639:Bicarbonates; D010848:Picolinic Acids; D011805:Quinolinic Acids; D001224:Aspartic Acid; D014364:Tryptophan; D008715:Methionine; C010981:homarine; D005990:Glycerol