| 生物活性： |
背景说明：Histatin 5 抑制宿主基质金属蛋白酶 MMP-2 和 MMP-9 活性，IC50 分别为 0.57 和 0.25 μM。
In Vitro：Histatin 5 is a member of a family of low-molecular-weight salivary proteins secreted by parotid， submandibular， and sublingual glands. Using biotinylated gelatin as a substrate， Histatin 5 inhibits the activity of the host matrix metalloproteinases MMP-2 and MMP-9 with IC50s of 0.57 and 0.25 μM， respectively. To localize the domain responsible for this inhibition， three peptides containing different regions of Histatin 5 are synthesized and tested as inhibitors of MMP-9. Peptides comprising residues 1 to 14 and residues 4 to 15 of Histatin 5 show much lower inhibitory activities (IC50， 21.4 and 20.5 μM， respectively)， while a peptide comprising residues 9 to 22 showed identical activity to Histatin 5 against MMP-9. Kinetic analysis of the inhibition of the Arg-gingipain reveals that Histatin 5 is a competitive inhibitor， affecting only the Km with a Ki of 15 μM.
Histatin 5 is an inhibitor of mitochondrial respiration.The human salivary antifungal peptide Histatin 5 is taken up by Candida albicans cells and associates intracellularly with mitochondria. Histatin 5 inhibits respiration of isolated C. albicans mitochondria as well as the respiration of intact blastoconidia in a dose and time-dependent manner. Histatin 5 at a concentration of 33 μM inhibits state 2 respiration.
参考文献：[1]. Gusman H， et al. Salivary histatin 5 is an inhibitor of both host and bacterial enzymes implicated in periodontaldisease. Infect Immun. 2001 Mar;69(3):1402-8.
[2]. Helmerhorst EJ， et al. The human salivary peptide histatin 5 exerts its antifungal activity through the formation ofreactive oxygen species. Proc Natl Acad Sci U S A. 2001 Dec 4;98(25):14637-42.
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