Document Detail


Properties of D-xylose isomerase from Streptomyces albus.
MedLine Citation:
PMID:  239628     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A partially purified D-xylose isomerase has been isolated from cells of Streptomyces albus NRRL 5778 and some of its properties have been determined. D-Glucose, D-xylose, D-ribose, L-arabinose, and L-rhamnose served as substrates for the enzyme with respective Km values of 86, 93, 350, 153, and 312 mM and Vmax values measuring 1.23, 2.9, 2.63, 0.153, and 0.048 mumol min per mg of protein. The hexose D-allose was also isomerized. The enzyme was strongly activated by 1.0 mM Mg2+ but only partially activated by 1.0 mM Co2+. The respective Km values for Mg2+ and Co2+ were 0.3 and 0.003 mM. Mg2+ and Co2+ appear to have separate binding sites on the isomerase. These cations also protect the enzyme from thermal denaturation and from D-sorbitol inhibition. The optimum temperature for ketose formation was 70 to 80 C at pH values ranging from 7 to 9. D-Sorbitol acts as a competitive inhibitor with a Ki of 5.5 mM against D-glucose, D-xylose, and D-ribose. Induction experiments, Mg2+ activation, and D-sorbitol inhibition indicated that a single enzyme (D-xylose isomerase) was responsible for the isomerization of the pentoses, methyl pentose, and glucose.
Authors:
S Sanchez; K L Smiley
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Applied microbiology     Volume:  29     ISSN:  0003-6919     ISO Abbreviation:  Appl Microbiol     Publication Date:  1975 Jun 
Date Detail:
Created Date:  1975-11-06     Completed Date:  1975-11-06     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7605802     Medline TA:  Appl Microbiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  745-50     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Arabinose / metabolism
Carbohydrate Epimerases* / metabolism
Cell-Free System
Cobalt / pharmacology
Enzyme Activation
Glucose / metabolism
Hydrogen-Ion Concentration
Magnesium / pharmacology
Rhamnose / metabolism
Ribose / metabolism
Soil Microbiology*
Sorbitol / pharmacology
Stereoisomerism
Streptomyces / enzymology*
Temperature
Xylose / metabolism
Chemical
Reg. No./Substance:
0/Xylose; 10485-94-6/Rhamnose; 147-81-9/Arabinose; 50-69-1/Ribose; 50-70-4/Sorbitol; 50-99-7/Glucose; 7439-95-4/Magnesium; 7440-48-4/Cobalt; EC 5.1.3.-/Carbohydrate Epimerases
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