Double-headed protease inhibitors from black-eyed peas. II. Structural studies by optical absorption and circular dichroism.

摘要: Two new double-headed protease inhibitors from black-eyed peas have amino acid compositions typical of the low molecular weight legume seeds. Black-eyed pea chymotrypsin and trypsin inhibitor (BEPCI) contains no tryptophan, 1 tyrosine, 14 half-cystines out 83 residues per monomer. (BEPTI) 75 The molar extinctions at 280 nm are 2770 for BEPCI 3440 BEPTI. single tyrosyl residue is very inaccessible to solvent in native BEPTI neutral pH titrates anomalously with an apparent pK = 12. Ionization tyrosine complete 13 hours above No heterogeneity local environment different subunits can be detected spectrophotometrically. large number cystine leads intense complex near-ultraviolet CD spectrum contributions regions 248 233 nm. An intact disulfide structure required appearance bands. unusually resistant denaturation when compared similar proteins high content. All observations consistent a far more rigid than protein.