New thiol protease inhibitors, estatins A and B, were isolated from the culture filtrate of Myceliophthora thermophila M4323. The basic, water-soluble inhibitors were characterized as having an agmatine, /m^-epoxysuccinic acid and L-phenylalanine or L-tyrosine moieties in the structure. The molecular formulas C18H25N5O5and C18H25N5O6for A and B were indicated by elemental analysis and fast atom bombardment MS. Estatins were specific inhibitors against thiol proteases such as papain, ficin and bromelain. They suppressed IgE antibody production in mice, but not IgG.Lowmolecular weight protease inhibitors are useful at least as medicines or reagents for research.During our screening for thiol protease-specific inhibitors, a fungal culture produced inhibitors against papain. The inhibitors were isolated and named estatins A and B (Fig.
Communications to the Editor ISOLATION AND CHARACTERIZATION OF SPOREAMICIN B Sir: Sporeamicin A is a 14-membered macrolide antibiotic produced by Saccharopolyspora sp. L53-18, which has strong antibacterial activity against Gram-positive bacteria.x~4) During the
Low molecular weight protease inhibitors are useful as medicines or reagents for research. During our screening for thiol protease-speciflc inhibitors from culture filtrates of microorganisms, we have succeeded in the isolation of new compounds, estatins A and B1}. Wehave further screened for inhibitors against cathepsin B, and discovered
Sporeamicin A is a new erythromycin-type antibiotic isolated from a species of Saccharopolyspora. It was active in vitro against a wide variety of Gram-positive bacteria. In vitro studies indicated that the sporeamicin A was stable in the presence of human serum, although it was bound to serum proteins. Sporeamicin A was effective in the mouse protection test against Staphylococcus aureus, Streptococcuspyogenes and Streptococcuspneumoniae. Sporeamicin A attained higher plasma and tissue levels in the rat than did erythromycin stearate.
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