Identification and characterization of N-acetyl-2,3-didehydro-2-deoxyneuraminic acid as a metabolite in mammalian brain.
We have identified N-acetyl-2,3-didehydro-2-deoxyneuraminic acid (NADNA) in bovine and in rat brain. Identification was made by mass spectrometric and gas-liquid chromatographic analysis of the per(trimethylsilyl) derivative of the purified brain compound. Central nervous system NADNA hitherto has escaped detection; it behaves chromogenically and chromatographically during purification on ion-exchange chromatography as free N-acetylneuraminic acid (NANA) that also occurs in brain. Although NADNA is a dehydro analogue of NANA, we have ascertained that brain NANA does not give rise to NADNA as an artifact during its purification from brain. Three hours after intracranial injection of [14C]-N-acetylmannosamine [( 14C]ManNAc), we detected [14C]NANA but no [14C]NADNA in rat brain. ManNAc is a brain NANA precursor, and at this time, formation of cytidine 5'-phosphate (CMP)-[14C]NANA from [14C]ManNAc is at a maximum. This finding precludes decomposition of CMP-NANA as a source of brain NADNA. Upon intracranial injection of [14C]ManNAc, [14C]NADNA became detectable at 19 h and reached a maximum level around 40 h later; this maximum of labeling of NADNA coincides with the maximum label in brain sialo conjugate-NANA. These findings clearly demonstrate the occurrence of NADNA in mammalian brain. From the evidence, NADNA may derive enzymatically from brain sialo conjugates.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D002417:Cattle; D002855:Chromatography, Thin Layer; D008401:Gas Chromatography-Mass Spectrometry; D006595:Hexosamines / Q000378:metabolism; D006865:Hydrogenation; D019158:N-Acetylneuraminic Acid / Q000031:analogs & derivatives*; D051381:Rats; D011919:Rats, Inbred Strains; D012794:Sialic Acids / Q000302:isolation & purification / Q000378:metabolism*
D006595:Hexosamines; D012794:Sialic Acids; C036137:2-deoxy-2,3-dehydro-N-acetylneuraminic acid; D019158:N-Acetylneuraminic Acid; C002022:N-acetylmannosamine