Blom H J, Boers G H, Trijbels J M, van Roessel J J, Tangerman A
Department of Medicine, University Hospital Nijmegen, The Netherlands.
Metabolism. 1989 Jun;38(6):577-82. doi: 10.1016/0026-0495(89)90220-5.
Methionine is supposed to be degraded via two known routes, the transsulfuration and the transamination pathways. In particular, patients with hypermethioninemia, due to a defect in the transsulfuration pathway, may catabolize significant amounts of methionine via the transamination pathway. In this study the relative amount of methionine degraded via the transamination pathway in 17 patients with homozygous homocystinuria, due to cystathionine synthase deficiency, was compared with 23 normal subjects, and with a patient with hypermethioninemia due to a deficiency in methionine adenosyltransferase. The homocystinuric patients and the normal subjects were studied in the fasting state as well as after methionine loading (0.1 g/kg body weight). It is concluded that in cystathionine synthase deficient patients, the transamination pathway is not quantitatively important in methionine degradation despite elevated methionine levels. This is in contrast to the patient with methionine adenosyltransferase deficiency, who catabolizes at least 20% of his dietary methionine via the transamination pathway.
甲硫氨酸被认为通过两条已知途径降解，即转硫途径和转氨途径。特别是，由于转硫途径缺陷而患有高甲硫氨酸血症的患者，可能通过转氨途径分解大量甲硫氨酸。在本研究中，将17例因胱硫醚合成酶缺乏而患有纯合子同型胱氨酸尿症的患者，与23名正常受试者以及1例因甲硫氨酸腺苷转移酶缺乏而患有高甲硫氨酸血症的患者，通过转氨途径降解的甲硫氨酸相对量进行了比较。对同型胱氨酸尿症患者和正常受试者在空腹状态以及甲硫氨酸负荷（0.1 g/kg体重）后进行了研究。得出的结论是，在胱硫醚合成酶缺乏的患者中，尽管甲硫氨酸水平升高，但转氨途径在甲硫氨酸降解中在数量上并不重要。这与甲硫氨酸腺苷转移酶缺乏的患者形成对比，后者通过转氨途径分解至少20%的膳食甲硫氨酸。
