TITLE	Purification and characterization of sucrose phosphate synthase from sweet potato tuberous roots
AUTHOR	Wei-Liang Chen Biochemistry Laboratory, Department of Agricultural Chemistry, National Taiwan University, 1 Roosevelt Road Section 4, Taipei, Taiwan 107, Republic of China Dong-Jiann Huang Biochemistry Laboratory, Department of Agricultural Chemistry, National Taiwan University, 1 Roosevelt Road Section 4, Taipei, Taiwan 107, Republic of China Pang-His Liu Biochemistry Laboratory, Department of Agricultural Chemistry, National Taiwan University, 1 Roosevelt Road Section 4, Taipei, Taiwan 107, Republic of China Heng-Long Wang Institute of Biological Chemistry, Academia Sinica, P.O. Box 23-106, Taiwan 107, Republic of China Jong-Ching Su Biochemistry Laboratory, Department of Agricultural Chemistry, National Taiwan University, 1 Roosevelt Road Section 4, Taipei, Taiwan 107, Republic of China Ping-Du Lee Biochemistry Laboratory, Department of Agricultural Chemistry, National Taiwan University, 1 Roosevelt Road Section 4, Taipei, Taiwan 107, Republic of China
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ABSTRACT	Sucrose phosphate synthase (SPS) is one of the key enzymes in the sucrose biosynthesis pathway. SPS was purified 40 fold from crude extract of sweet potato tuberous roots by the methods of batch elution from DEAE-Sephacel, PEG precipitation, w-aminohexyl Sepharose 4B affinity and Mono Q anion exchange chomatographies. The native- and SDS-PAGE analyses revealed SPS to have a native molecular mass of about 540 kDa, and it may therefore be homotetramer composed of subunit with a mass of 130-140 kDa. The isoelectric point of the purified enzyme as determined by IEF was 5.29. SPS from the sweet potato tuberous root, which differs from the SPS of photosynthetic tissues, was not allosterically regulated by G6P and Pi. The Km for F6P and UDPG was 5.3 and 31.3 mM, respectively. The enzyme was activated by Mn2+, Mg2+, and Ca2+, while being inhibited by Hg2+. The nucleotides AMP, ADP, ATP, UMP, UDP, UTP, and TDP inhibited the enzyme about 30~50%. The enzyme was sensitive to sulfydryl reagents, but activity could be restored with DTT or b-ME. The enzyme was activated by glucose, glucosamine, maltose, and lactose, but was inhibited by d-gluconolactone. SPS could also be inhibited by PCMBS and Cibacron blue F3G-A.
KEYWORD	Enzyme purification; Ipomoea batatas; Sucrose metabolism; Sucrose phosphate synthase; Sweet potato;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 42 Number 2 April 2001, page 123-129, 7 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China