PURIFICATION AND PHYSICOCHEMICAL PROPERTIES OF β‐GALACTOSIDASE FROM Kluyveromyces fragilis
1978
MAHONEY, R. R. | WHITAKER, J. R.
An enzyme of value for cheese whey utilization was purified from a microorganism that is a good source and is itself approved for use in foods. β-Galactosidase was purified to apparent homogeneity from cell-free extracts of K. fragilis by acetone precipitation, pseudoaffinity chromatography, hydroxylapatite chromatography and DEAE-Sephadex A-50 chromatography. The mol. wt. was 201 000 and the partial specific vol. was 0.715. No carbohydrate was detected. Electron microscopy indicated a molecular diam. of about 16 nm with 9-10 subunits present. Isoelectric point of the major isozyme was 5.1. The extinction coeff. was 1.58 cm2/mg protein at 280 nm. The amino-acid composition was quite different from the β-galactosidase of Escherichia coli. Enzyme activity was rapidly lost on incubation with p-chloromercuribenzoate; formation of 5-6 mol mercaptide/mol protein gave complete loss of activity.
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