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Proteolysis of αs1-casein by chymosin: influence of pH and urea

Published online by Cambridge University Press:  01 June 2009

D. M. Mulvihill  and
P. F. Fox
D. M. Mulvihill
Affiliation:
Department of Food Chemistry, University College, Cork, Irish Republic
P. F. Fox
Affiliation:
Department of Food Chemistry, University College, Cork, Irish Republic
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Summary

The specificity of chymosin on αs1-casein was shown to be dependent on the reaction pH and on the state of aggregation of the substrate. In aqueous solution αs1-casein was optimally hydrolysed to αs1-I at pH 5·8; if the casein was solubilized in the isoelectric region by the use of 5 M-urea, optimum proteolysis occurred at pH 2·8. Hydrolysis of αs1-I to yield αs1-II, αs1-III and αs1-IV occurred at pH values > 5·8 in the presence or absence of urea. In the isoelectric region αs1-II, αs1-III and αs1-IV were not formed in the absence of urea where the substrate was aggregated: instead a peptide αs1-V was produced; at the same pH and using urea as a solubilizing agent αs1-II, αs1-III and αs1-IV were formed together with a further peptide αs1-VI.

Type
Original Articles
Information
Journal of Dairy Research , Volume 44 , Issue 3 , October 1977 , pp. 533 - 540
Copyright
Copyright © Proprietors of Journal of Dairy Research 1977

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References

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