ISSN:
1573-4919
Keywords:
Hex A
;
Hex B
;
N-acetyl-glucosaminidases
;
kinetics
;
thermodynamic transitions
;
ion-exchangers
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Summary The kinetic and thermodynamic properties of N-acetyl-β-D-glucosaminidase A (Hex A) and N-acetyl-β-D-D-glucosaminidase β (Hex B) from goat testes were investigated in free and bound (after binding them on ion-exchangers such as DEAE- or CM-cellulose respectively) forms. The optimum pH of free Hex A and Hex B was at 4.2 and 5.4, whereas the bound forms showed the optimum pH at 4.0 and 5.2 respectively. While apparent Km of free and bound Hex A (0.8 and 1.0 mM respectively) did not differ, the Km of Hex B increased when bound on CM-cellulose (Km of free Hex B = 0.96 mM versus bound Hex B = 1.6 mM). Though the free Hex A was more thermo-labile than the free Hex B, both isozymes, on insoluble matrices decayed at faster rates on heating. Activation analysis revealed that the energy of activation (E infa supo ) for transition state of free Hex B (81 Kcal deg−1 mole−1) did not differ from E infa supo of bound Hex B. On the other hand, E infa supo of free Hex A declined from 77.2 to 71.1 Kcal deg−1 mole−1 when heat transitions were carried out in free and bound state respectively. Thermodynamic analysis suggested a change in entropy of activation (ΔS*) of free Hex A and Hex B as 200 and 211 eu respectively. While ΔS* of Hex B did not change after heat transitions, ΔS* of Hex A was 182.5 eu.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00231690
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