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Query: UMLS:C0022568 (keratitis)
 5,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To get a better understanding of the possible role of proteases in the pathogenesis of fungal keratitis, the extracellular proteases of a clinical isolate of Aspergillus flavus, from a severe case of keratitis, were identified and partially characterized. This strain, designated CU226/88, was grown with a variety of substrates as nitrogen sources, under conditions that would be expected to derepress the production of extracellular proteases. When grown on minimal medium with milk protein as a nitrogen source, the fungus appeared to produce primarily a metalloprotease, which has a zinc cofactor. When grown with insoluble collagen or elastin as a nitrogen source, a serine protease and cysteine protease, as well as the metalloprotease, are produced. Strain CU226/88 can grow with collagen, but not elastin, as the sole source of carbon as well as nitrogen. It is possible that the collagenase activity is a mediator of the severe corneal destruction caused by this isolate.
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PMID:Extracellular proteases of Aspergillus flavus. Fungal keratitis, proteases, and pathogenesis. 217 95

Acanthamoeba species are frequently isolated from soil and water collections. In the environment, the organisms multiply as phagotrophic trophozoites and encyst under adverse conditions. Several species are known to infect man, causing keratitis and opportunistic diseases. The mechanisms underlying tissue damage and invasion by the amoebae are being elucidated and the involvement of secreted peptidases, particularly serine peptidases, has been demonstrated. Here, elastase activity was examined in Acanthamoeba-conditioned medium (ACM), making use of elastin-Congo red (ECR) and synthetic peptide p-nitroanilide substrates. ACM hydrolysed ECR over a broad pH range and optimally at a pH of 7.5 and above. Indicating the activity of serine and metallopeptidases, Congo red release was potently inhibited by PMSF, antipain, chymostatin and 1,10-phenanthroline, partially reduced by elastatinal and EDTA, and unaffected by 1,7-phenanthroline and E-64. Screening with synthetic substrates mainly showed the activity of serine peptidases. ACM efficiently hydrolysed Suc-Ala(2)-Pro-Leu-pNA and Suc-Ala(2)-Pro-Phe-pNA over a broad pH range (7.0-9.5) and was weakly active against Suc-Ala(3)-pNA, a substrate found to be optimally hydrolysed at a pH around 7.0. Following ammonium sulfate precipitation of ACM proteins and FPLC analysis, the majority of the ECR-splitting activity, characterised as serine peptidases, bound to CM-sepharose and co-eluted with part of the Suc-Ala(2)-Pro-Phe-pNA-hydrolysing activity in a gradient of 0-0.6M NaCl. In the corresponding FPLC fractions, serine peptidases resolving in the region of 70-130kDa were detected in gelatin gels. Overall, the results demonstrate that trophozoites secrete elastases, and additionally suggest the high molecular weight serine peptidases as possible elastase candidates.
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PMID:Elastase secretion in Acanthamoeba polyphaga. 1963 88