Purification, Identification and Characterization of Aspartic Proteases of Chicken Intestine

Abstract

Chicken intestine, an underutilized by-product of poultry industry is a rich source of tissue proteases, especially aspartic proteases. Two of the major aspartic proteases of the tissue were purified from lysosomal and post lysosomal fractions and identified by N-terminal amino acid sequencing as cathepsin D and pepsin, respectively. The enzymes differed in their molecular and biochemical properties like molecular weight, optimum conditions for protein degradation and stability in different conditions of pH and temperature. Both enzymes were completely inhibited by pepstatin. The kinetic constant, Km for chicken intestinal pepsin and cathepsin D (for haemoglobin substrate) were estimated to be 6.45 μM and 22.7 μM, respectively. The interaction of both enzymes with different food proteins suggests pepsin could be used in applications demanding extensive hydrolysis of proteins, while cathepsin D could be used in those needing controlled degradation of proteins. Practical Applications Chicken intestine is a by-product of poultry industry. The tissue could serve as a major source of proteases especially aspartic proteases, which can be used as an alternative for proteases currently used in food industries. Aspartic proteases (pepsin and cathepsin D) from this tissue can be recovered and used for preparation of protein hydrolysates in a more economical way. Furthermore, the byproduct can be exploited to increase revenues for poultry processors.