Orjih A U
MLS Department, Faculty of Allied Health Sciences, Kuwait University, Salaibikhat 90805, Kuwait.
Exp Biol Med (Maywood). 2001 Sep;226(8):746-52. doi: 10.1177/153537020222600806.
The ferriprotoporphyrin IX (FP) molecules released by intraerythrocytic malaria parasites during hemoglobin digestion are converted to beta-hematin and are stored in the parasites' food vacuoles. It has been demonstrated in cell-free medium that the incorporation of FP into beta-hematin under physiological conditions requires a catalyst from parasite lysates or pre-formed beta-hematin. In the present studies, lysates of Plasmodium falciparum-infected erythrocytes were suspended in 1 M NaOH and were washed with phosphate buffer, pH 7.6. When the cell extracts were incubated with hematin in 0.5 M sodium acetate buffer, pH 5, for 20 hr at 37 degrees C, a large quantity of beta-hematin was formed. To determine whether parasite components were necessary for the beta-hematin formation, normal erythrocyte ghosts were similarly treated with 1 M NaOH and then incubated with hematin. In repeated experiments it was found that, on the average, 70% of the hematin was converted to beta-hematin. Membranes treated with HCl or CH(3)COOH also promoted the formation of beta-hematin, while untreated membranes were ineffective. The possibility that metabolic activities in the food vacuoles of malaria parasites may activate membrane fragments, from hemoglobin vesicles, to promote beta-hematin formation is discussed in this paper.
红细胞内疟原虫在消化血红蛋白过程中释放的亚铁原卟啉IX（FP）分子会转化为β-血红素，并储存于疟原虫的食物泡中。在无细胞培养基中已证实，在生理条件下将FP掺入β-血红素需要来自寄生虫裂解物的催化剂或预先形成的β-血红素。在本研究中，将恶性疟原虫感染的红细胞裂解物悬浮于1 M NaOH中，并用pH 7.6的磷酸盐缓冲液洗涤。当细胞提取物在pH 5的0.5 M醋酸钠缓冲液中与血红素于37℃孵育20小时时，会形成大量的β-血红素。为确定寄生虫成分对于β-血红素形成是否必要，对正常红细胞血影进行类似的1 M NaOH处理，然后与血红素孵育。在重复实验中发现，平均而言，70%的血红素转化为β-血红素。用HCl或CH(3)COOH处理的膜也促进β-血红素的形成，但未处理的膜则无效。本文讨论了疟原虫食物泡中的代谢活动可能激活来自血红蛋白囊泡的膜片段以促进β-血红素形成的可能性。
