Chemical Modification of Avian Ovomucoids^*

Abstract

Comparative physical and chemical studies were performed on three avian qvomucoids: chicken ovomucoid (a trypsin inhibitor), turkey ovomucoid (a trypsin and chymotryps ininhibitor), and pheasant ovomucoid (a chymotrypsin inhibitor). The amino acid composition and the carbohydrate contents have been determined. All three ovomucoids are stable to heating a t 80 ' at pH < 9, but heating to 100 O at p H 6 or to 80 O a t pH 9 results in a rapid loss of inhibitory activity for all three ovomucoids. They are also resistant to treatment with trichloroacetic acidacetone and 9 M urea a t 80 ' . Their complexes with the respective enzymes are not affected by 3 M urea. Acetylation with acetic anhydride or carbamylation with KNCO destroy the trypsin inhibitory activity of turkey ovomucoid, while they leave its chymotrypsin inhibitory activity and the inhibitory activities of the other ovomucoids unaffected. It appeared that the structural requirements of turkey and chicken ovomucoids for inhibiting trypsin are different and that the inhibitory sites of turkey ovomucoid for trypsin and for chymotrypsin are independent.Extensive iodination has no effect on any of the inhibitory activities.

N-Acetylimidazole: A Reagent for Determination of “Free” Tyrosyl Residues of Proteins*

“…Tyrosyl acetylation was determined from the decrease in molar absorptivity using a factor of 1160 per tyrosyl residue per mole, as described in the text. 9 Hermans (1962).c Crammer and Neuberger (1943).d Havsteen and Hess (1962).6 Stevens and Feeney (1963). zShugar (1952); Tanford et ai (1955a).0 Inada etal.…”

Determination of Antigenicity by Radioimmunoassay and of Trypsin Inhibitory Activities in Heat or Enzyme Denatured Ovomucoid

“…Lineweaver and Murry (1947) demonstrated that the ovomucoid heated at 80°C for 30 min in an acidic or neutral solution retained more than 90% of the activity. Stevens and Feeney (1963) found that 30% of the activity still remained after heating the protein at 100°C for 15 min at pH 6. Fraenkel-Conrat et al (1952) showed that 80% and 62% of the activity remained when the ovomucoid was heated at 90°C for 15 min at pH 5 and pH 7, respectively.…”

Inhibition of Porcine Elastase by Turkey Ovomucoid and Chicken Ovoinhibitor

“…ovomucoid and 1.6 for chicken ovoinhibitor. Molar ratios of inhibitor to enzyme calculated by assuming the molecular weight of 28000 for turkey ovomucoid [27], 46500 for chicken ovoinhibitor [17] and 25800 [l] for porcine elastase are 0.92 and 0.89 respectively which indicate 1 : 1 molar complex. The formation of complexes between elastase and both inhibitors was further demonstrated by means of electrophoresis.…”