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NUMBER AND NATURE OF THE SULPHYDRYL GROUPS OF β‐GALACTOSIDASE FROM KLUYVEROMYCES FRAGILIS
Author(s) -
MAHONEY R. R.
Publication year - 1980
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.1980.tb00657.x
Subject(s) - dtnb , dithiothreitol , chemistry , biochemistry , enzyme , stereochemistry , glutathione
The β‐ galactosidase from Kluyveromyces fragilis contains 6 sulphydryl groups, all of which are modified by 5,5‐ dithiobis (2‐ nitrobenzoic acid) (DTNB) before all activity is lost. Activity losses can be largely (> 70%) reversed by dithiothreitol when the number of sulphydryls reacted is 4 or less. Kinetic studies with DTNB suggest that none of the sulphydryls are in the active site, but that their modification leads to changes in the tertiary structure of the enzyme and hence gradual loss of activity.