Preamylopectin processing: a mandatory step for starch biosynthesis in plants

• Published in: The Plant cell Vol. 8; no. 8; pp. 1353 - 1366
• Main Authors: Mouille, G. (Universite des Sciences et Technologie de Lille, Villeneuve, France.), Maddelein, M.L, Libessart, N, Talaga, P, Decq, A, Delrue, B, Ball, S
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Physiologists 01.08.1996
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; ALMIDON; AMIDON; AMILOPECTINA; AMYLOPECTINE; Biosynthesis; Branching; Chlamydomonas; CHLAMYDOMONAS REINHARDTII; Corn; DEXTRINAS; DEXTRINE; Dextrins; Enzymes; Freshwater; Gels; GENE; GENES; GLUCANE; GLUCANOS; Glucans; HIDROLASAS; HIDROLISIS; HYDROLASE; HYDROLYSE; LOCI; LOCUS; METABOLISME DES GLUCIDES; METABOLISMO DE CARBOHIDRATOS; Plant cells; Plants; POLISACARIDOS; POLYHOLOSIDE; Starches
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.8.8.1353

It has been generally assumed that the alpha-(1 leads to 4)-linked and alpha 1 leads to 6)-branched glucans of starch are generated by the coordinated action of elongation (starch syntheses) and branching enzymes. We have identified a novel Chlamydomonas locus (STA7) that when defective loads to a wipeout of starch and its replacement by a small amount of glycogen-like material. Our efforts to understand the enzymological basis of this phenotype have led us to determine the selective disappearance of an 88-kD starch hydrolytic activity. We further demonstrate that this enzyme is a debranching enzyme. Cleavage of the alpha-(1 leads to 6) linkage in a branched precursor of amylopectin (preamylopectin) has provided us with the ground rules for understanding starch biosynthesis in plants. Therefore, we propose that amylopectin clusters are synthesized by a discontinuous mechanism involving a highly specific glucan trimming mechanism