Jamjoom Ghazi A
College of Applied Medical Sciences, and King Fahd Medical Research Center, King Abdulaziz University, Jeddah, P.O. Box 415 Jeddah 21411, Saudi Arabia.
Malariaworld J. 2017 Aug 1;8:10. eCollection 2017.
Hemozoin is generally considered a waste deposit that is formed for the sole purpose of detoxification of free heme that results from the digestion of hemoglobin by parasites. However, several observations of parasite multiplication, both in vertebrate and invertebrate hosts are suggestive of a wider, but overlooked, metabolic role for this product. The presence of clinical peripheral blood samples of with high parasitemia containing only hemozoin-deficient (non-pigmented) asexual forms has been repeatedly confirmed. Such samples stand in contrast with other samples that contain mostly pigmented circulating trophozoites and gametocytes, indicating that pigment accumulation is a prominent feature of gametocytogenesis. The restricted size, i.e. below detection by light microscopy, of hemozoin in asexual merozoites and ringforms of implies its continuous turnover, supporting a role in metabolism. The prominent interaction of hemozoin with several antimalarial drugs, the involvement of proteins in hemozoin formation, and the finding of plasmodial genes coding for a heme-oxygenase-like protein argue for a wider and more active role for hemozoin in the parasite's metabolism. The observed association of hemozoin with crystalloids during ookinete development is consistent with a useful function to it during parasite multiplication in the invertebrate host. Finally, alternative mechanisms, other than hemozoin formation, provide substitute or additional routes for heme detoxification.
疟色素通常被认为是一种废物沉积物，其形成的唯一目的是对寄生虫消化血红蛋白产生的游离血红素进行解毒。然而，在脊椎动物和无脊椎动物宿主中对寄生虫增殖的一些观察结果表明，这种产物具有更广泛但被忽视的代谢作用。临床外周血样本中高疟原虫血症且仅含有缺乏疟色素（无色素）的无性形态，这一现象已被反复证实。此类样本与其他主要含有色素化循环滋养体和配子体的样本形成对比，表明色素积累是配子体形成的一个显著特征。无性裂殖子和环状体中疟色素的尺寸受限，即低于光学显微镜检测水平，这意味着其不断更新，支持了其在代谢中的作用。疟色素与几种抗疟药物的显著相互作用、蛋白质参与疟色素形成以及发现编码类血红素加氧酶蛋白的疟原虫基因，都表明疟色素在寄生虫代谢中具有更广泛且更活跃的作用。在动合子发育过程中观察到疟色素与晶体的关联，这与它在无脊椎动物宿主中寄生虫增殖期间的有用功能是一致的。最后，除了疟色素形成之外的其他机制为血红素解毒提供了替代或额外途径。
