Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand.
Exp Parasitol. 2011 Oct;129(2):115-9. doi: 10.1016/j.exppara.2011.07.006. Epub 2011 Jul 14.
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.
在 L3 和成虫捻转血矛线虫和环形泰勒虫中检测到完全功能的鸟氨酸-谷氨酸-脯氨酸途径，使寄生虫能够相互转化这些氨基酸。鸟氨酸转氨酶（OAT）（EC 2.6.1.13）是一种可逆的吡哆醛-5-磷酸（PLP）依赖性酶，最适 pH 值为 8.5。羟胺完全抑制了两种寄生虫中的 OAT 活性。对于所有五种酶，每个物种和生命周期阶段的底物亲和力相似，显著的例外是在成年环形泰勒虫中，Δ（1）-吡咯啉-5-羧酸（P5C）还原酶（EC 1.5.1.2）对 P5C 的亲和力降低近 10 倍，L3 捻转血矛线虫的 P5C 脱氢酶（EC 1.5.1.12）对 P5C 的亲和力降低约一半。P5C 合酶（EC 1.2.1.41）的活性与 NADPH 或 NADH 作为辅酶相似。脯氨酸氧化酶（EC 1.5.99.8）是一种不需要辅酶的酶，最适 pH 值为 8.5。尽管与宿主中的酶相似，但如果这些酶在抗原上存在差异，它们仍然可以作为控制目标，因为脯氨酸的供应对于角质层的形成是必要的。
