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  • Title: Comparison of the substrate conformations in the active sites of papain, chymopapain, ficin and bromelain by resonance Raman spectroscopy.
    Author: Carey PR, Ozaki Y, Storer AC.
    Journal: Biochem Biophys Res Commun; 1983 Dec 28; 117(3):725-31. PubMed ID: 6365089.
    Abstract:
    The resonance Raman spectra of several enzyme-substrate intermediates of papain, chymopapain, ficin and bromelain are reported. The intermediates are dithioacyl enzymes formed during the catalyzed hydrolysis of N-acylglycine thionoester substrates. Interpretation of the resonance Raman spectra allows us to compare, for the first time, the substrate geometries in a series of functioning intermediates from different enzymes. The substrates assume essentially identical conformations for papain, chymopapain and ficin and a similar, but not identical, conformation in the active site of bromelain. Each dithioacyl enzyme population appears to be made up of a single homogeneous conformational state. This state has been characterised in earlier studies of dithioacyl papains. It is designated as conformer B and is characterized by an attractive contact between the substrate's glycinic N atom and the active site cysteine S atom. It is now apparent that conformer B is of general significance in the mechanism of cysteine proteases.
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