Enzymatic synthesis and characterization of alpha-hydroxy acid and amino acid co-oligomers

Methionine and lysine are considered the primary limiting amino acids in most animals and need to be supplemented in the feed. Ruminants possess a pre-gut fermentative step, where the supplements are converted to short chain fatty acids and ammonia. As a result, orally administered crystalline amino acid and peptides are not bioavailable to the animal. The alpha-hydroxy analog of methionine, HMB (2-hydroxy-4-(methylthio)butanoic acid) has been used as an unconventional source of methionine supplementation. HMB has been reported to be more resistant to ruminal degradation than methionine and is readily converted to methionine via stereospecific amination pathways. To take advantage of HMB resistance to rumen microbial attack and enhance amino acid availability, administration of HMB-capped amino acid oligomers has been considered. However, such oligomers are not available. The present study was undertaken to explore enzymatic the synthesis and characterization of HMB and amino acid co-oligomers.;Papain-catalyzed synthesis of HMB-capped hydrophobic amino acid oligomers was evaluated in buffers at different pH conditions. The synthesis of HMB-capped hydrophilic amino acid oligomers with papain was explored with a two-phase and a novel three-phase system. The oligomers were purified and characterized with reverse phase liquid chromatography (RPLC) and liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). The oligomers were also analyzed with matrix assisted-time of flight mass spectrometry (MALDI-TOF-MS). The result showed that HMB can be readily incorporated in polypeptide chains.