Pyridoxal phosphate de-activation by pyrroline-5-carboxylic acid - Increased risk of vitamin B-6 deficiency and seizures in hyperprolinemia type II

We previously identified vitamin B-6 deficiency in a child presenting with seizures whose primary diagnosis was the inherited disorder hyperprolinemia type II. This is an unrecognized association, which was not explained by d iet or medication. We hypothesized that pyridoxal phosphate (vitamin B-6 co enzyme) was de-activated by L-Delta (1)-pyrroline-5-carboxylic acid, the ma jor intermediate that accumulates endogenously in hyperprolinemia type II. The proposed interaction has now been investigated in vitro with high resol ution H-1 nuclear magnetic resonance spectroscopy and mass spectrometry at a pH of 7.4 and temperature of 310 K. Three novel adducts were identified. These were the result of a Claisen condensation (or Knoevenagel type of rea ction) of the activated C-4 carbon of the pyrroline ring with the aldehyde carbon of pyridoxal phosphate. The structures of the adducts were confirmed by a combination of high performance liquid chromatography, nuclear magnet ic resonance, and mass spectrometry. This interaction has not been reported before. From preliminary observations, pyrroline-5-carboxylic acid also co ndenses with other aromatic and aliphatic aldehydes and ketones, and this m ay be a previously unsuspected generic addition reaction. Pyrroline-5 carbo xylic acid is thus found to be a unique endogenous vitamin antagonist. Vita min B-6 de-activation may contribute to seizures in hyperprolinemia type II , which are so far unexplained, but they may be preventable with long term vitamin B-6 supplementation.