Proteolytic specificity of chymosin on caprine alpha s1-caseins A and F.
From hydrolysis experiments carried out on alpha s1-caseins A and F at pH 5.2 in the presence of 30 g NaCl/l, i.e. the conditions encountered in many young goats' cheeses, it was found that minima of 19 and 9 bonds were sensitive to chymosin in variants A and F respectively. Variant A was hydrolysed faster than variant F and the proteolytic pattern (reversed-phase HPLC and polyacrylamide agarose gel electrophoresis) differed between the variants. Hydrolysates from both variants had a number of cleavage sites in common (Leu20-Leu21, Phe23-Ala24 and Phe32-Arg33 in both variants, Leu101-Lys102 and Leu64-Lys65, Leu120-His121 and Leu83-His84, Leu142-Ala143 and Leu105-Ala106, Leu149-Phe150 and Leu112-Phe113, Leu156-Asp157 and Leu119-Asp120, Trp164-Tyr165 and Trp127-Tyr128 in variants A and F respectively), while other bonds were split only in variant A (Leu16-Asn17, Glu18-Asn19, Phe28-Pro29, Ile44-Gly45, Tyr80-Ile81, Gln82-Lys83, Tyr91-Leu92, Tyr94-Leu95, Leu109-Glu110 and Phe179-Ser180). Major cleavage sites appeared to be at Phe23-Val24, Leu142-Ala143 and Trp164-Tyr165 for variant A, and Phe23-Val24 and Leu64-Lys65 for variant F. Cleavage site Phe23-Val24 could be the origin of the first breakdown product from goat alpha s1-caseins A and F visible in polyacrylamide agarose gel electrophoresis.
Trujillo
A J
AJ
Centre Especial de Recerca en Tecnologia dels Aliments (CeRTA), Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra, España.
Miranda
G
G
Lebars
D
D
Delacroix-Buchet
A
A
D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D002611:Cheese; D002851:Chromatography, High Pressure Liquid; D012085:Chymosin / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D014644:Genetic Variation; D006041:Goats; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D013379:Substrate Specificity
D002364:Caseins; D010446:Peptide Fragments; D012085:Chymosin