School of Dentistry, Institute of Clinical Sciences, University of Liverpool, Liverpool, UK.
Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool, UK.
Mol Oral Microbiol. 2018 Aug;33(4):322-335. doi: 10.1111/omi.12229.
Streptococcus gordonii, an accessory pathogen and early colonizer of plaque, co-aggregates with many oral species including Porphyromonas gingivalis. It causes α-hemolysis on blood agar, a process mediated by H O and thought to involve concomitant oxidation of hemoglobin (Hb). Porphyromonas gingivalis has a growth requirement for heme, which is acquired mainly from Hb. The paradigm for Hb heme acquisition involves the initial oxidation of oxyhemoglobin (oxyHb) to methemoglobin (metHb), followed by heme release and extraction through the actions of K-gingipain protease and/or the HmuY hemophore-like protein. The ability of S. gordonii to mediate Hb oxidation may potentially aid heme capture during co-aggregation with P. gingivalis. Hemoglobin derived from zones of S. gordonii α-hemolysis was found to be metHb. Generation of metHb from oxyHb by S. gordonii cells was inhibited by catalase, and correlated with levels of cellular H O production. Generation of metHb by S. gordonii occurred through the higher Hb oxidation state of ferrylhemoglobin. Heme complexation by the P. gingivalis HmuY was employed as a measure of the ease of heme capture from metHb. HmuY was able to extract iron(III)protoporphyrin IX from metHb derived from zones of S. gordonii α-hemolysis and from metHb generated by the action of S. gordonii cells on isolated oxyHb. The rate of HmuY-Fe(III)heme complex formation from S. gordonii-mediated metHb was greater than from an equivalent concentration of auto-oxidized metHb. It is concluded that S. gordonii may potentially aid heme acquisition by P. gingivalis by facilitating metHb formation in the presence of oxyHb.
戈登链球菌是一种附属病原体和菌斑的早期定植菌，与许多口腔物种（包括牙龈卟啉单胞菌）共同聚集。它在血琼脂上引起α-溶血，这一过程由 H O 介导，被认为涉及血红蛋白（Hb）的同时氧化。牙龈卟啉单胞菌有对血红素的生长需求，血红素主要从 Hb 中获得。Hb 血红素获取的范例涉及初始氧化氧合血红蛋白（oxyHb）为高铁血红蛋白（metHb），随后通过 K-牙龈蛋白酶和/或 HmuY 血红素样蛋白的作用释放和提取血红素。S. gordonii 介导 Hb 氧化的能力可能有助于在与 P. gingivalis 共同聚集期间捕获血红素。从 S. gordonii α-溶血区衍生的血红蛋白被发现为 metHb。S. gordonii 细胞通过过氧化氢酶抑制从 oxyHb 生成 metHb，并与细胞 H O 产生水平相关。S. gordonii 通过高铁血红蛋白的更高 Hb 氧化状态产生 metHb。使用 P. gingivalis HmuY 对血红素的络合作为从 metHb 中容易捕获血红素的量度。HmuY 能够从 S. gordonii α-溶血区衍生的 metHb 和 S. gordonii 细胞作用于分离的 oxyHb 生成的 metHb 中提取铁（III）原卟啉 IX。从 S. gordonii 介导的 metHb 形成的 HmuY-Fe(III)血红素络合物的形成速率大于从等量的自动氧化 metHb。结论是，S. gordonii 可能通过在 oxyHb 存在下促进 metHb 的形成，从而帮助 P. gingivalis 获得血红素。
