Enzymic mechanism of starch breakdown in germinating rice seeds V. Sucrose phosphate synthetase in the scutellum |
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Authors: | Nomura Tokeo; Akazawa T |
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Institution: | Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University Chikusa, Nagoya, 464 Japan |
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Abstract: | Some enzymic Properties of a partially purified preparationof sucrose phosphate synthetase (E.C.2.4.1.14) from germinatingrice seed scutella were studied. Examination of the reactionkinetics revealed that the rate of synthesis of sucrose phosphatefollows the Michaelis-Menten equation at an optimum PH of 7.5,having Km of 25 mM for UDP-glucose, and of 4.9 mM for fructose6-phosphate. UDP inhibited the enzyme reaction competitively;K1 of 3.3 mM. Fe++ and Fe+++ activated the enzyme reaction about2-fold; Ka, 0.3 mM and 2.0 mM, respectively. Co++, Co(NH3)6+++,Mg++ and Mn++ also activated the enzyme reaction. At high concentrationK+ activated the enzyme reaction with the maximum activationof 24% at 400 mM. The molecular weight and S20,w value of theenzyme were determined as 4.5 ? 105 and 10.4S, respectively.
1Part IV of this series is Ref. (5).
2California Foundation for Biochemical Research Fellow (1973). (Received December 20, 1973; ) |
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