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evolution
subunit ISA1 is a family 13 glycoside hydrolase, which has activity for hydrolyzing alpha-1,6-glucosidic linkages corresponding to branch points of growing amylopectin molecules
evolution
subunit ISA2 is a family 13 glycoside hydrolase, but its putative catalytic residues are altered, rendering it enzymatically inactive. Despite its inactivity, ISA2 is evolutionarily conserved in plants, and has been suggested to play a role as a regulatory subunit for ISA1
evolution
B6U0X5
the enzyme belongs to the glycosyl hydrolase family 13 GH13, and harbors a carbohydrate-binding module family 48 (CBM48) domain
evolution
B6U0X5
the enzyme belongs to the glycosyl hydrolase family 13 GH13, and harbors a carbohydrate-binding module family 48 (CBM48) domain
evolution
the enzyme harbors a carbohydrate-binding module family 48 (CBM48) domain
evolution
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subunit ISA2 is a family 13 glycoside hydrolase, but its putative catalytic residues are altered, rendering it enzymatically inactive. Despite its inactivity, ISA2 is evolutionarily conserved in plants, and has been suggested to play a role as a regulatory subunit for ISA1
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evolution
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subunit ISA1 is a family 13 glycoside hydrolase, which has activity for hydrolyzing alpha-1,6-glucosidic linkages corresponding to branch points of growing amylopectin molecules
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evolution
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the enzyme harbors a carbohydrate-binding module family 48 (CBM48) domain
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malfunction
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both overexpression and loss of function of isoamylase 3 in the endosperm generated pleomorphic amyloplasts and starch granules
malfunction
loss of isozyme ISA1 or ISA2 causes phytoglycogen accumulation
malfunction
mutants of the STA8 locus accumulate both phytoglycogen and a reduced amount of high amylose starch
malfunction
mutation of the STA7 locus leads to a very severe reduction of starch content and its replacement by a water-soluble polysaccharide phytoglycogen
malfunction
B6U0X5
the ISA1 homomer does not provide the full physiological function of ISA activity in maize leaves. This is in contrast to the endosperm, where loss of ISA2, and thus the ISA1/ISA2 heteromeric enzyme, can be tolerated without major defects. Mutants without ISA2 differ in leaf starch content, granule morphology, and amylopectin structure compared with nonmutants or lines lacking both ISA1 and ISA2, mutant phenotypes, overview
malfunction
B6U0X5
the ISA1 homomer does not provide the full physiological function of ISA activity in maize leaves. This is in contrast to the endosperm, where loss of ISA2, and thus the ISA1/ISA2 heteromeric enzyme, can be tolerated without major defects. Mutants without ISA2 differ in leaf starch content, granule morphology, and amylopectin structure compared with nonmutants or lines lacking both ISA1 and ISA2. Plastids from maize leaves lacking ISA2 exhibit a nearly normal appearance with the exception that starch granules appear to be slightly smaller than in wild-type, mutant phenotypes, overview
malfunction
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seeds of the homozygous mutants, cr-isa1-1 (type 1, with an adenine insertion) and cr-isa1-2 (type 3, with a cytosine deletion) display a shrunken endosperm with significantly lower grain weight. Abnormal starch granules and amyloplasts are found in cr-isa1-1 and cr-isa1-2 endosperm cells. The contents of total starch, amylose and amylopectin in the endosperm of the cr-isa1 mutants are significantly reduced, whereas sugar content and starch gel consistency were observably increased compared to the wild type. The gelatinization temperature and starch chain length distributions of the cr-isa1 mutants are also altered. The transcript levels of most starch synthesis-related genes are significantly lower in cr-isa1 mutants
malfunction
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mutants of the STA8 locus accumulate both phytoglycogen and a reduced amount of high amylose starch
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malfunction
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mutation of the STA7 locus leads to a very severe reduction of starch content and its replacement by a water-soluble polysaccharide phytoglycogen
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physiological function
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isoamylase 3 facilitates starch metabolism and affects morphological characteristics of plastids in rice. Both overexpression and loss of function of isoamylase 3 in the endosperm generates pleomorphic amyloplasts and starch granules
physiological function
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the isoamylase 1 is essential for amylopectin biosynthesis and starch production in rice endosperm. Overexpression of the isoamylase 2 gene brings about a dramatic reduction in kernel size in the dry seed and the transformants contain less than 50% of the starch in the kernel, while the content of soluble sugars, including maltodextrins, malto-oligosaccharides, and simple sugars, increase by about 8fold when compared with the host cultivar Kinmaze
physiological function
the isoamylase ISA1/ISA2 heteromeric complexes II and III are not required in maize endosperm for normal starch content and structure, and the ISA1 homomeric complex is sufficient for most ISA functions. ISA1 is required for the accumulation of ISA2, which is regulated posttranscriptionally, while the absence of ISA2 in isa2-339 mutants has no effect on the accumulation of ISA1 mRNA or protein
physiological function
isoamylase catalyzes hydrolysis of alpha-D-(1,6)-glucosidic branch linkages in amylopectin and glycogen to release amylose and linear maltooligosaccharides
physiological function
starch debranching enzymes isoamylase 1 and 2, ISA1 and ISA2, are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. The function of the complex is to remove misplaced branches of growing amylopectin molecules, which would otherwise prevent the association and crystallization of adjacent linear chains
physiological function
starch debranching enzymes isoamylase 1 and 2, ISA1 and ISA2, are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. The function of the complex is to remove misplaced branches of growing amylopectin molecules, which would otherwise prevent the association and crystallization of adjacent linear chains. ISA2 plays a role as a regulatory subunit for ISA1
physiological function
the ISA1 class of DBE is the one primarily associated with amylopectin synthesis
physiological function
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starch debranching enzymes isoamylase 1 and 2, ISA1 and ISA2, are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. The function of the complex is to remove misplaced branches of growing amylopectin molecules, which would otherwise prevent the association and crystallization of adjacent linear chains. ISA2 plays a role as a regulatory subunit for ISA1
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physiological function
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starch debranching enzymes isoamylase 1 and 2, ISA1 and ISA2, are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. The function of the complex is to remove misplaced branches of growing amylopectin molecules, which would otherwise prevent the association and crystallization of adjacent linear chains
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physiological function
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isoamylase catalyzes hydrolysis of alpha-D-(1,6)-glucosidic branch linkages in amylopectin and glycogen to release amylose and linear maltooligosaccharides
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additional information
Arabidopsis thaliana subunit ISA1 requires subunit ISA2 as a partner for enzymatic function. Images of purified starch granules of wild-type and mutant lines, overview
additional information
Arabidopsis thaliana subunit ISA1 requires subunit ISA2 as a partner for enzymatic function. Images of purified starch granules of wild-type and mutant lines, overview
additional information
Arabidopsis thaliana subunit ISA1 requires subunit ISA2 as a partner for enzymatic function. Images of purified starch granules of wild-type and mutant lines, overview. Recombinant AtISA1 is capable of enzymatic activity if mixed with recombinant AtISA2 but does not display such function on its own
additional information
Arabidopsis thaliana subunit ISA1 requires subunit ISA2 as a partner for enzymatic function. Images of purified starch granules of wild-type and mutant lines, overview. Recombinant AtISA1 is capable of enzymatic activity if mixed with recombinant AtISA2 but does not display such function on its own
additional information
isozyme ISA1 interacts with its homologue ISA2, but no evidence for interaction with other starch biosynthetic enzymes. ISA1 and ISA2 form a heteromultimeric enzyme with ISA1 being the catalytic subunit and ISA2 subunit not catalytically active
additional information
isozyme ISA1 interacts with its homologue ISA2, but no evidence for interaction with other starch biosynthetic enzymes. ISA1 and ISA2 form a heteromultimeric enzyme with ISA1 being the catalytic subunit and ISA2 subunit not catalytically active
additional information
subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo
additional information
subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo
additional information
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subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo
additional information
subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo. Subunit ISA1 enzyme is also partially functional without subunit ISA2
additional information
subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo. Subunit ISA1 enzyme is also partially functional without subunit ISA2
additional information
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subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo. Subunit ISA1 enzyme is also partially functional without subunit ISA2
additional information
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Zea mays subunit ISA1 is active by itself and does not require subunit ISA2 for activity, subunit ISA 2 alone is catalytically inactive
additional information
B6U0X5
Zea mays subunit ISA1 is active by itself and does not require subunit ISA2 for activity, subunit ISA 2 alone is catalytically inactive
additional information
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Zea mays subunit ISA1 is active by itself, either in vitro or in transgenic Arabidopsis leaves, and does not require subunit ISA2 for activity
additional information
B6U0X5
Zea mays subunit ISA1 is active by itself, either in vitro or in transgenic Arabidopsis leaves, and does not require subunit ISA2 for activity
additional information
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subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo
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additional information
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subunit ISA2 interacts physically with ISA1, presence of both homomeric ISA1 and heteromeric ISA1-ISA2 complexes in vivo. Subunit ISA1 enzyme is also partially functional without subunit ISA2
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additional information
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Arabidopsis thaliana subunit ISA1 requires subunit ISA2 as a partner for enzymatic function. Images of purified starch granules of wild-type and mutant lines, overview. Recombinant AtISA1 is capable of enzymatic activity if mixed with recombinant AtISA2 but does not display such function on its own
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additional information
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Arabidopsis thaliana subunit ISA1 requires subunit ISA2 as a partner for enzymatic function. Images of purified starch granules of wild-type and mutant lines, overview
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