Properties of enzymes involved in D-galactonate catabolism in fungi
| Autor: | Mokhtar S. Ammar, Osama M. Abdel-Fatah, Ali M. Elshafei, Salah M. Mohawed |
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| Rok vydání: | 1995 |
| Předmět: |
Protein Denaturation
Galactonate dehydratase Stereochemistry Glyceraldehyde Microbiology chemistry.chemical_compound Deoxy Sugars Enzyme Stability Ketoses Pyruvic Acid Magnesium Aspergillus terreus Pyruvates Molecular Biology Hydro-Lyases Aldehyde-Lyases chemistry.chemical_classification biology Chemistry Aldolase A Temperature Sugar Acids General Medicine Metabolism Hydrogen-Ion Concentration biology.organism_classification Kinetics Metabolic pathway Aspergillus Enzyme Biochemistry Dehydratase biology.protein |
| Zdroj: | Antonie van Leeuwenhoek. 67:211-216 |
| ISSN: | 1572-9699 0003-6072 |
| DOI: | 10.1007/bf00871215 |
| Popis: | Two enzymes catalyze the two step reactions in the D-galactonate nonphosphorolytic catabolic pathway of Aspergillus terreus, namely D-galactonate dehydratase and 2-keto-3-deoxy-D-galactonate (KDGal) aldolase. Maximum enzyme activities were obtained at 40 degrees C and pH 8.0 or at 50 degrees C and pH 7.5 for these two enzymes, respectively. Stability of the two enzymes under different conditions was investigated. From a Lineweaver-Burk plot of the reciprocal of initial velocities and substrate concentrations, apparent Km values were calculated for D-galactonate, pyruvate and glyceraldehyde and found to be 8.33, 14.28 and 5.55 mM, respectively, in crude cell-free extracts. Results indicated the requirement of magnesium cation for D-galactonate dehydratase activity at an initial concentrations of 10(-2) M. The presence of Mg2+ in the reaction mixture seems to induce greatly the fitness of the dehydratase with D-galactonate as no activity could be detected with 24-h dialyzed extract in the absence of magnesium cation. |
| Databáze: | OpenAIRE |
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