ADPG formation by the ADP‐specific cleavage of sucrose‐reassessment of sucrose synthase

FEBS Letters

Akazawa, Takashi¹  Pozueta-Romero, Javier¹  Yamaguchi, Junji¹ 

[1] Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University, Chikusa, Nagoya 464-01, Japan

关键词: ADP-glucose;    Starch biosynthesis;    Sucrose metabolism;    Sucrose synthase;    UDP-glucose;    ADPG;    ADP-glucose;    HK;    hexokinase;    NBT;    p-nitrobluetetrazolium;    NDP (NTP);    nucleoside diphosphate (tiphosphate);    6PGDH;    6-P-gluconate dehydrogenase;    PGI;    P-glucoisomerase;    SS;    sucrose synthase;    UDPG;    UDP-glucose;   

DOI  :  10.1016/0014-5793(91)81292-G

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The standardized enzyme coupling method for assaying sucrose synthase activities in the direction of sucrose cleavage was reexamined using enzyme preparations from cultured cells of sycamore (Acer pseudoplatanus L.) and spinach leaves (Spinacea oleracea). Both ATP and Tris, commonly utilized in assay systems to measure sucrose synthase, were found to inhibit non-competitively the ADPG-synthesizing activities of the enzyme. Upon substituting ATP by either GTP or UTP, and Tris by HEPES, we found that the sucrose synthase is capable of producing ADPG effectively, recognizing ADP as the principal substrate (K _m = 5.3 μM (sycamore) and 16.8 μM (spinach)). The V _max value for the synthesis of ADPG clearly surpasses the V _max observed for the synthesis of UDPG by the enzyme, It was found that UDP is not inhibitory on the synthesis of ADPG by SS, which behaves allosterically with respect to the concentration level of sucrose.

【 授权许可】

Unknown