[Key enzymes in starch synthesis in plants].
Starch, the most common form of stored carbon in plants, is both the major food source for mankind and important raw material for many industries. It is composed of two types of alpha-1,4-linked glucan polymer: essentially unbranched amylose and regularly branched amylopectin, and synthesized in photosynthetic and non-photosynthetic organs. Starch is synthesized via four committed enzyme steps: ADP-Glc pyrophosphorylase, which synthesizes sugar nucleotide precursors; starch synthase, which extends the alpha-1,4-linked glucan chains using ADP-Glc; starch-branching enzymes, which introduce alpha-1,6 branch points to form amylopectin; and starch debranching enzymes, which hydrolyze alpha-1,6 branches in glucans. In this paper, recent advances in biochemical characterizations and gene engineering concerning these enzymes were reviewed, and the achievements in gene engineering involved in manipulation of starch amount and quality were also cited.
Kang
Guo-Zhang
GZ
National Engineering Research Centre for Wheat, Henan Agricultural Unerversity, Zhengzhou 450002, China. kangguozhang@eyou.com
Wang
Yong-Hua
YH
Guo
Tian-Cai
TC
Zhu
Yun-Ji
YJ
Guan
Chun-Yun
CY
D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D005959:Glucosidases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D006004:Glycogen Debranching Enzyme System / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010944:Plants / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D013213:Starch / Q000096:biosynthesis* / Q000378:metabolism; D013214:Starch Synthase / Q000235:genetics / Q000378:metabolism / Q000502:physiology
D006004:Glycogen Debranching Enzyme System; D013213:Starch; D015061:1,4-alpha-Glucan Branching Enzyme; D013214:Starch Synthase; D051599:Glucose-1-Phosphate Adenylyltransferase; D005959:Glucosidases