Influence of γ-radiation on the structure and function of soybean trypsin inhibitor.

Soybean trypsin inhibitor (STI) is a known antinutrient and food allergen present in soybean. γ-Radiation has the potential to inactivate the TI protein. However, a systematic study on the influence of different moisture levels during γ radiation on structure and function of the molecule has not been reported. Pure STI was irradiated up to 200 kGy, in dry state, with 50% moisture and in aqueous solution. The radiation damage in molecular structure was assessed using, SDS-PAGE, size exclusion chromatography, fluorescence measurement, and circular dichroism, while functional damage was assessed by the TI assay. In aqueous solution, both the structure and function of TI were almost destroyed at the 10 kGy dose. While with 50% moisture and in dry state, the loss in functional and structural attributes was discernible only at 30 and 100 kGy, respectively. The TI activity was found to be unaffected in dry and soaked seeds of soybean as well as other legumes up to irradiation doses of 100 and 50 kGy, respectively.

A rapid autolytic method for the preparation of protein hydrolysate from poultry viscera.

Protein hydrolysate was prepared from poultry viscera by a procedure involving autolysis for 6h at pH 2.8 and 55 degrees C followed by heat inactivation, filtration and drying. Recovery of nitrogen in the product was 87%. The process reduced the viable count of bacteria by 5-6logcfu/g. The product contained 84% protein, 6.5% ash and 8.8% moisture. Peptide analysis by gel filtration chromatography showed size in the range of 0.5-5kDa. RPHPLC exhibited the presence of hydrophilic peptides in higher concentration than that in trypsin digest of casein. Protein hydrolysate exhibited presence of all essential amino acids in comparison with reference protein except for methionine and threonine. The product possesses excellent solubility (>93%) over a pH range of 1-12. Efficacy of the product as a bacteriological media or feed supplement is discussed.

Autolytic degradation of chicken intestinal proteins.

Data on the exhaustive degradation of chicken intestinal proteins by endogenous proteases, which could be utilized as a means to prepare protein hydrolysate, is reported in the present paper. Chicken intestine possesses proteolytic activities (cathepsin B, D, H, L, aminopeptidases and alkaline proteases) comparable to that in organ tissues like liver and spleen, which could degrade the tissue proteins extensively. The autolytic degradation was found to be optimum at pH 2.5 and 60 degrees C. Analysis by SDS-PAGE showed a time dependent degradation of proteins to low molecular weight (<10 kDa) products. Kinetic studies employing specific inhibitors indicated that the degradation (90-94%) of proteins at acidic pH is governed largely by pepstatin sensitive proteases. The acidic extract of the tissue was found to hydrolyse albumin, casein and soybean proteins efficiently. Results point to the possible application of tissue autolysis for obtaining protein hydrolysates from chicken intestine. Chicken intestine could also serve as a potential source of much needed proteolytic enzymes for food and pharmaceutical applications.

Identification and purification of an aspartic proteinase from human semen.

To purify and evaluate the molecular changes associated with an aspartic protease (Cathepsin D) in human semen from infertile subjects. Cathepsin D was purified from normo-, oligo- and azoospermic semen, by a procedure involving detergent solubilisation, affinity chromatography and gel filtration chromatography. The enzyme from normo-, oligo- and azoospermic samples was purified 86, 60 and 44 fold respectively. The purified enzyme appeared as a single band on SDS as well as on native PAGE irrespective of the pathological conditions. The molecular weight of Cathepsin D from oligospermic and normospermic samples was 40 kDa while that of azoospermic sample was found to be 43 kDa. The enzyme was inhibited by pepstatin while other proteinase inhibitors and metal ions did not have any effect. Purified Cathepsin D from azoospermic sample differs from normospermia and oligospermia.