title: A low-molecular-mass aspartic protease inhibitor from a novel Penicillium sp.: implications in combating fungal infections.
abstract: A low-molecular-mass aspartic protease inhibitor was isolated from a novel Penicillium sp. The inhibitor was purified to homogeneity, as shown by reversed-phase HPLC and SDS-PAGE. The M(r) of the inhibitor was 1585 and the amino acid composition showed the presence of D, D, D, E, A, K, L, Y, H, I and W residues. The steady-state kinetic interactions of Aspergillus saitoi aspartic protease with the inhibitor revealed the reversible, competitive, time-dependent tight-binding nature of the inhibitor, with IC(50) and K(i) values of 1.8 and 0.85 µM, respectively. Fluorescence spectroscopy and circular dichroism analysis showed that inactivation of the enzyme was due to binding of the inhibitor to the active site. The inhibitor was found to inhibit mycelial growth and spore germination of Aspergillus fumigatus and Aspergillus niger in vitro with MIC values of 1.65 and 0.30 µg ml(-1), respectively. This study will potentially open the way towards the development of a tight-binding peptidic inhibitor against fungal aspartic proteases to combat human fungal infections.
authors.affiliation: Division of Biochemical Sciences, National Chemical Laboratory, Pune 411 008, India.
authors.forename: Vishnu
authors.initials: V
authors.lastname: Menon
authors.affiliation: Division of Biochemical Sciences, National Chemical Laboratory, Pune 411 008, India.
authors.forename: Mala
authors.initials: M
authors.lastname: Rao
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D057055:Aspartic Acid Proteases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D001232:Aspergillus fumigatus / Q000187:drug effects / Q000254:growth & development; D001234:Aspergillus niger / Q000187:drug effects / Q000254:growth & development; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D020128:Inhibitory Concentration 50; D007700:Kinetics; D008969:Molecular Sequence Data; D010407:Penicillium / Q000201:enzymology* / Q000235:genetics; D011480:Protease Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013050:Spectrometry, Fluorescence
chemical_list: D000935:Antifungal Agents; D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D011480:Protease Inhibitors; D057055:Aspartic Acid Proteases