Journal article
Yeast hexokinase. IV. Multiple forms of hexokinase in the yeast cell
Biochemistry (Easton), Vol.10(19), pp.3499-3508
09/01/1971
DOI: 10.1021/bi00795a003
PMID: 4947783
Abstract
Using improved methods for the preparation of hexokinase from baker's yeast without autolysis by any of the yeast proteases, the extract was shown to contain four hexokinase isoenzymes, A, A', B, and C, and a specific glucokinase. The latter is extracted in a form having molecular weight about one million. Other active hexokinase species, arising by proteolysis of native forms, are distinct frorn these, and are sup-pressed when initial removal of proteases is efficient. Conditions are described for obtaining hexokinases A, B, and C in pure form, each homogeneous in starch gel electrophoresis. Hexokinases A and B are the previously described forms, and differ in that A has a greater relative activity on fructose, a lower specific activity, and a higher negative charge (at pH above 5) than B. Their measured activity differences are essentially a reflection of differences in the Michaelis-Menten maximum velocities on glucose and on fructose. Hexokinase C is a newly described isoenzyme, identical with B in most properties but having a different mobility in anion-exchange chromatography. It can be converted to B when a high ionic strength is applied at pH 4.6 or 8, followed by gel filtration. Immediately upon rupture, yeast cell lysates contain most or all of their hexokinase B in the form of C. Also present in the fresh lysates is hexokinase A', which appears to be a hybrid of A and B. This hybrid splits to give A and B in the conditions of purification. The course of release of the hexokinases was followed in the melting of frozen yeast. Sixty per cent of the total activity was readily liberated as soluble forms, these being characterized as A, A', and C. The remainder is probably osmotically trapped in the cell debris, and is not bound to the cell walls. © 1971, American Chemical Society. All rights reserved.
Details
- Title: Subtitle
- Yeast hexokinase. IV. Multiple forms of hexokinase in the yeast cell
- Creators
- Eric A BarnardArmin H RamelYoucef M RustumJ. Gareth Jones
- Resource Type
- Journal article
- Publication Details
- Biochemistry (Easton), Vol.10(19), pp.3499-3508
- Publisher
- American Chemical Society
- DOI
- 10.1021/bi00795a003
- PMID
- 4947783
- ISSN
- 0006-2960
- eISSN
- 1520-4995
- Language
- English
- Date published
- 09/01/1971
- Academic Unit
- Hematology, Oncology, and Blood & Marrow Transplantation; Internal Medicine
- Record Identifier
- 9984359827102771
Metrics
9 Record Views