Chichibabin Pyridine Synthesis - Evidence of This Mechanism in-vivo

Evidence of This Mechanism in-vivo

In vivo, deamination of the α-amino group of amino acids produces small amounts of ammonia. Researchers found that protein-incorporated allysine, (deaminated lysine) from bovine ligamentum nuchae elastin fibers appeared to be pyridine cross-linked. The structures of these cross-linked amino acids had 3,4,5- and 2,3,5-trisubstituted pyridine skeletons, specifically pyridinated desmosine (DESP) and pyridinated isodesmosine (IDP).

Extrapolating from an in-vitro elastin model under physiological conditions, the researchers found that the ratios of IDP to DESP corresponded extremely closely with values based on both a calculation of a theoretical Chichibabin pyridine synthesis of 3 mol allysine and 1 mol ammonia, and reported ratios of 2,3,5- to 3,4,5-trisubstituted pyridine ratios of a Chichibabin pyridine synthesis involving phenylacetaldehyde. They concluded with relative certainty that the pyridine cross-links found in elastin were, in fact, due to an in-vitro Chichibabin pyridine synthesis of ammonia and allysine.