Jan 1, 1995

Properties of enzymes involved in D-galactonate catabolism in fungi

Antonie van Leeuwenhoek
A M ElshafeiO M Abdel-Fatah

Abstract

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.

Mentioned in this Paper

Aspergillus terreus antigen
Galactonate Dehydratase Activity
galactonic acid, monopotassium salt
Biochemical Pathway
Aspergillus terreus allergenic extract
Enzymes, antithrombotic
Aldehyde-Lyases
Pyruvate Measurement
Catabolic Process
Glyceraldehyde

About this Paper

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