| Autor: |
H M, Fernandez-Lahore, R M, Auday, E R, Fraile, M, Biscoglio de Jimenez Bonino, L, Pirpignani, C, Machalinski, O, Cascone |
| Rok vydání: |
1999 |
| Předmět: |
|
| Zdroj: |
The journal of peptide research : official journal of the American Peptide Society. 53(6) |
| ISSN: |
1397-002X |
| Popis: |
The fourth-day extract of a solid-state culture of the mesophilic Mucor sp. (M-105) strain showed a high milk-clotting activity and a clotting/proteolytic activity ratio similar to that of commercial preparations from microbial origin used in cheese manufacture. After ultrafiltration of the crude extract, the milk-clotting proteinase was purified in two steps: ion-exchange followed by size-exclusion chromatography. Enzyme homogeneity was assessed by HPLC, SDS-PAGE and N-terminal residue determination. A pI value of 4.21 was obtained and a molecular weight of 33 kDa was calculated from size-exclusion chromatography and SDS-PAGE data. The optimum pH for proteolytic activity towards dimethylcasein was in the 3.0-3.5 range. The proteinase retained 26 and 13% of its proteolytic activity after a 30-min incubation period, at pH 5.0 and 50 and 60 degrees C, respectively. This evidenced a lower heat stability than that of the thermophilic enzymes currently used in the cheese industry and also than that of bovine chymosin. The enzyme was fully inhibited by pepstatin A and no effect was observed with PMSF, p-CMPS or EDTA. The N-terminal amino acid sequence: GTGTVPVTDDGNLNEYYXTVTVGXP was compared with those from other fungal enzymes. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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