PURIFICATION AND PROPERTIES OF A TRANSKETOLASE RESPONSIBLE FOR FORMALDEHYDE FIXATION IN A METHANOL-UTILIZING YEAST, CANDIDA-BOIDINII (KLOECKERA SP) NO 2201

  • 1 January 1982
    • journal article
    • research article
    • Vol. 715  (2) , 143-150
Abstract
Dihydroxyacetone synthase, present in methanol-grown C. boidinii (Kloeckera sp.) no. 2201, catalyzes the transfer of the glycolaldehyde group from xylulose 5-phosphate to formaldehyde to form glyceraldehyde 3-phosphate and dihydroxyacetone. This enzyme was purified to electrophoretic homogeneity and found to be a new type of transketolase. The MW of the enzyme was estimated to be 190,000 by gel filtration. The enzyme appeared to be composed of 4 identical subunits (MW, 55,000). Thiamin pyrophosphate and Mg2+ were required for the activity. The optimum pH was found to be 7.0. With xylulose 5-phosphate as the ketol-donor, aliphatic aldehydes (C1-C7), glycoaldehyde and glyceraldehyde were better acceptors than ribose 5-phosphate. The kinetic data were consistent with a ping-pong bi-bi mechanism. The Km values obtained were as follows: xylulose 5-phosphate, 1.0 mM; formaldehyde, 0.43 mM; glyceraldehyde 3-phosphate, 0.42 mM; and dihydroxyacetone, 0.52 mM.

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