Biomedical Engineering Reference
In-Depth Information
Table 9.2 Major starch pathway enzymes and respective genes
Starch biosynthetic
enzyme
Protein
abbreviation
Comm.
specialty
Maize gene
Chromosome
Starch effect
Sucrose synthase
Sus
shrunken-1
9S
Not used
Little or no starch produced
ADP-glucose pyrophosphorylase - heterotetramer
Large subunit
AGPase LS
shrunken-2
3L
Sweet corn
Little or no starch produced
Small subunit
AGPase SS
brittle-2
4S
Not used
Little or no starch produced
ADP-glucose
translocator
ADPGluc
transporter
brittle-1
5L
Not used
Little or no starch produced.
Starch debranching
enzymes
ISAI or DBE
sugary-1
4S
Sweet corn
Phytoglycogen predominantly produced with very little starch
Soluble starch synthases
SSIIa
sugary-2
6L
Waxy
Causes a reduction in amylopectin and results in higher amylose.
Reduces amylopectin chain length in combination with GBSS
SSIII
dull-1
10L
Not used
Reduced activity of SBEIIb
Granule-bound starch
synthase
GBSSI
waxy-1
9S
Waxy
Endosperm starch content is approximately 100 % amylopectin
Starch branching enzymes
SBEIIb
amylose-
extender
5L
Amylose
Increased amylose content to 45-55 %
SBEI
sbe-1
5S
Amylose
Increases amylopectin branching, in combination with SBEIIb
elevates amylose content
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