Studies on the possibility of histidine biosynthesis from histidinol, imidazolepyruvic acid, imidazoleacetic acid, and imidazolelactic acid by mixed ruminal bacteria, protozoa, and their mixture in vitro

摘要: The possibility of histidine (His) synthesis using a main biosynthetic pathway involving histidinol (HDL) and also the recycling capability imidazolic compounds such as imidazolepyruvic acid (ImPA), imidazoleacetic (ImAA), imidazolelactic (ImLA) to produce His were investigated mixed ruminal bacteria (B), protozoa (P), mixture both (BP) in an vitro system. Rumen microorganisms anaerobically incubated at 39°C for 18 h with or without each substrate (2 mM) mentioned. other related produced supernatants hydrolyzates incubation analyzed by high-performance liquid chromatography. B, P, BP suspensions failed show synthesizing ability when HDL. was synthesized from ImPA BP. Expressed units "per gram microbial nitrogen (MN)", disappearance greatest B (72.7 µmol/g MN per hour), followed (33.13 hour) then P (18.6 18-h period. production (240.0, 275.9, 261.2 6, 12, incubation, respectively) about 3.5 times higher than that (67.3, 83.8, 72.7 respectively). Other metabolites ImLA, ImAA, histamine (HTM), urocanic (URA), found all suspensions. ImLA remained diminution Although ImAA be degraded small extent (3.4–6.3%) only after neither nor detected on chromatograms. These results have been demonstrated first time rumen suggest may essential amino microorganisms.