Enzymes of the ornithine-glutamate-proline pathway in the sheep abomasal nematode parasites Haemonchus contortus and Teladorsagia circumcincta

Experimental Parasitology
S UmairH V Simpson

Abstract

A fully functional ornithine-glutamate-proline pathway was detected in L3 and adult Haemonchus contortus and Teladorsagia circumcincta, making the parasites capable of interconversion of these amino acids. Ornithine aminotransferase (OAT) (E.C. 2.6.1.13) was a reversible pyridoxal-5-phosphate (PLP)-dependent enzyme with an optimum pH 8.5. Hydroxylamine completely inhibited OAT activity in both parasites. For all five enzymes, substrate affinity was similar for each species and life cycle stage, the notable exceptions being the nearly 10-fold lower affinity for Δ(1)-pyrroline-5-carboxylate (P5C) of P5C reductase (E.C. 1.5.1.2) in adult T. circumcincta and about half for P5C for L3 H. contortus P5C dehydrogenase (E.C. 1.5.1.12). P5C synthase (E.C. 1.2.1.41) activity was similar with either NADPH or NADH as co-factor. Proline oxidase (E.C. 1.5.99.8) was a co-factor independent enzyme with an optimal pH 8.5. Despite similarities to those in the host, enzymes of this pathway may still be useful as control targets if they differ antigenically, as a supply of proline is necessary for cuticle formation.

References

Nov 10, 1998·The Biochemical Journal·G Wu, S M Morris
Jun 14, 2003·Journal of Insect Physiology·P Y Scaraffia, M A Wells
Apr 5, 2005·Insect Biochemistry and Molecular Biology·Patricia Y ScaraffiaMichael A Wells
Mar 1, 1974·Plant Physiology·A D McNamer, C R Stewart

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Citations

Feb 5, 2013·Experimental Parasitology·S UmairH V Simpson
Dec 14, 2011·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·Saleh UmairHeather V Simpson
Mar 31, 2012·Experimental Parasitology·S UmairH V Simpson

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