title: A novel pyrroline-5-carboxylic acid and acetoacetic acid adduct in hyperprolinaemia type II.
abstract: BACKGROUND
  From investigations of a child with hyperprolinaemia type II, we demonstrated in vitro that pyridoxal phosphate forms a novel adduct with a proline metabolite, pyrroline-5-carboxylic acid, through Claisen condensation. Studies indicated that this was a previously unsuspected generic reaction of aldehydes and some ketones. We have subsequently found the acetoacetic acid adduct in both plasma and urine from the affected child.
  
  
  METHODS
  Mixtures of acetoacetic acid and pyrroline-5-carboxylic acid were co-incubated at pH 7.4 and 37 degrees C, dried, or extracted and dried, derivatised and analysed by gas chromatography/mass spectrometry (GC/MS). Urine and plasma from the child were analysed.
  
  
  RESULTS
  Fourteen new peaks were found in derivatised pyrroline-5-carboxylic acid/acetoacetic acid co-incubates. From accurate molecular mass data, the four largest peaks were probably diastereoisomers of tri-trimethylsilyl (tri-TMS) derivatives of alcohol adducts formed by Claisen condensation. Eight other peaks were mono- and di-trimethylsilyl derivatives of the adduct and a decarboxylated product. The adduct was demonstrated unequivocally in the child's acute urine and traces in plasma.
  
  
  CONCLUSIONS
  Pyrroline-5-carboxylic acid forms an adduct with acetoacetic acid, which was present in urine of a sick child with hyperprolinaemia type II. Evidence suggests it formed in vivo. The biological significance of this novel reaction of aldehydes and ketones merits investigation.
authors.affiliation: Department of Chemical Pathology, Southampton General Hospital, Level D, Mail Point 6, Tremona Road, Southampton, SO16 6YD, UK. Valeire.walker@suht.swest.nhs.uk
authors.forename: Valerie
authors.initials: V
authors.lastname: Walker
authors.forename: Graham A
authors.initials: GA
authors.lastname: Mills
authors.forename: John M
authors.initials: JM
authors.lastname: Mellor
authors.forename: G John
authors.initials: GJ
authors.lastname: Langley
authors.forename: R Duncan
authors.initials: RD
authors.lastname: Farrant
mesh_terms: D000090:Acetoacetates / Q000097:blood / Q000378:metabolism* / Q000652:urine; D000592:Amino Acid Metabolism, Inborn Errors / Q000097:blood / Q000378:metabolism* / Q000652:urine; D002648:Child; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D011392:Proline / Q000097:blood / Q000378:metabolism*; D011732:Pyridoxal Phosphate / Q000378:metabolism; D011758:Pyrroles / Q000097:blood / Q000378:metabolism* / Q000652:urine; D013237:Stereoisomerism
chemical_list: D000090:Acetoacetates; D011758:Pyrroles; C015485:delta-1-pyrroline-5-carboxylate; C016635:acetoacetic acid; D011732:Pyridoxal Phosphate; D011392:Proline