Amino acid biosynthesis in Haemonchus contortus from C14-labelled precursors, in vitro

Adult Haemonchus contortus (Nematoda: Trichostrongylidae) was investigated for its ability to utilize various C14-labelled precursors, i.e., glucose, acetate, CO2 and palmitic acid, for amino acid biosynthesis. H. contortus has been demonstrated to be capable of synthesizing essential as well as non-essential amino acids. Label from all the precursors was detected in aspartic acid, lysine, histidine, cystine, cysteine, glutamic acid, proline, arginine, tyrosine, alanine, glycine, serine, valine, methionine, leucine and isoleucine. Glutamic acid, aspartic acid, alanine, glycine and serine were synthesized to a greater extent relative to the other amino acids, regardless of the precursor employed. However, in case of glucose, there was comparatively less incorporation into glycine and serine. Incorporation of C14 into various amino acids is evidence for the operation of tricarboxylic acid cycle. Further, the fact that carbon from palmitic acid appears in amino acids, indicates that adult H. contortus is capable of catabolizing long-chain fatty acids. Possible mechanisms for the involvement of various precursors in amino acids biosynthesis are examined here.