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Three isoforms of isoamylase contribute different catalytic properties for the debranching of potato glucans

Three isoforms of isoamylase contribute different catalytic properties for the debranching of potato glucans
Three isoforms of isoamylase contribute different catalytic properties for the debranching of potato glucans

Isoamylases are debranching enzymes that hydrolyze α-1,6 linkages in α-1,4/α-1,6-linked glucan polymers. In plants, they have been shown to be required for the normal synthesis of amylopectin, although the precise manner in which they influence starch synthesis is still debated. cDNA clones encoding three distinct isoamylase isoforms (Stisa1, Stisa2, and Stisa3) have been identified from potato. The expression patterns of the genes are consistent with the possibility that they all play roles in starch synthesis. Analysis of the predicted sequences of the proteins suggested that only Stisa1 and Stisa3 are likely to have hydrolytic activity and that there probably are differences in substrate specificity between these two isoforms. This was confirmed by the expression of each isoamylase in Escherichia coil and characterization of its activity. Partial purification of isoamylase activity from potato tubers showed that Stisa1 and Stisa2 are associated as a multimeric enzyme but that Stisa3 is not associated with this enzyme complex. Our data suggest that Stisa1 and Stisa2 act together to debranch soluble glucan during starch synthesis. The catalytic specificity of Stisa3 is distinct from that of the multimeric enzyme, indicating that it may play a different role in starch metabolism.

1040-4651
133-149
Hussain, Hasnain
d382145f-3509-40e6-95d5-1eae93fd49f0
Mant, Alexandra
63319e45-deeb-45ad-a30d-e05b42052a0d
Seale, Robert
cfcbc732-fd94-4afd-82ff-272ef7a102f9
Zeeman, Sam
df8307f5-550a-4200-b7e8-725ded98591d
Hinchliffe, Edward
879406ec-c56a-4d60-8cc2-a7b629a614ad
Edwards, Anne
2df0b540-425b-41cc-b6c1-07e8096c9d04
Hylton, Christopher
ef9a8119-118a-48b1-9a16-35e823379d42
Bornemann, Stephen
407c12f0-27b7-49bc-8a11-0b2fb7d61d5b
Smith, Alison M.
6e9e908e-6c05-4cab-9b87-17d58061115a
Martin, Cathie
11f56167-8930-40eb-8222-745988fa43e3
Bustos, Regla
ac3bacf4-8d74-479a-919f-e1174e6db13f
Hussain, Hasnain
d382145f-3509-40e6-95d5-1eae93fd49f0
Mant, Alexandra
63319e45-deeb-45ad-a30d-e05b42052a0d
Seale, Robert
cfcbc732-fd94-4afd-82ff-272ef7a102f9
Zeeman, Sam
df8307f5-550a-4200-b7e8-725ded98591d
Hinchliffe, Edward
879406ec-c56a-4d60-8cc2-a7b629a614ad
Edwards, Anne
2df0b540-425b-41cc-b6c1-07e8096c9d04
Hylton, Christopher
ef9a8119-118a-48b1-9a16-35e823379d42
Bornemann, Stephen
407c12f0-27b7-49bc-8a11-0b2fb7d61d5b
Smith, Alison M.
6e9e908e-6c05-4cab-9b87-17d58061115a
Martin, Cathie
11f56167-8930-40eb-8222-745988fa43e3
Bustos, Regla
ac3bacf4-8d74-479a-919f-e1174e6db13f

Hussain, Hasnain, Mant, Alexandra, Seale, Robert, Zeeman, Sam, Hinchliffe, Edward, Edwards, Anne, Hylton, Christopher, Bornemann, Stephen, Smith, Alison M., Martin, Cathie and Bustos, Regla (2003) Three isoforms of isoamylase contribute different catalytic properties for the debranching of potato glucans. The Plant Cell, 15 (1), 133-149. (doi:10.1105/tpc.006635).

Record type: Article

Abstract

Isoamylases are debranching enzymes that hydrolyze α-1,6 linkages in α-1,4/α-1,6-linked glucan polymers. In plants, they have been shown to be required for the normal synthesis of amylopectin, although the precise manner in which they influence starch synthesis is still debated. cDNA clones encoding three distinct isoamylase isoforms (Stisa1, Stisa2, and Stisa3) have been identified from potato. The expression patterns of the genes are consistent with the possibility that they all play roles in starch synthesis. Analysis of the predicted sequences of the proteins suggested that only Stisa1 and Stisa3 are likely to have hydrolytic activity and that there probably are differences in substrate specificity between these two isoforms. This was confirmed by the expression of each isoamylase in Escherichia coil and characterization of its activity. Partial purification of isoamylase activity from potato tubers showed that Stisa1 and Stisa2 are associated as a multimeric enzyme but that Stisa3 is not associated with this enzyme complex. Our data suggest that Stisa1 and Stisa2 act together to debranch soluble glucan during starch synthesis. The catalytic specificity of Stisa3 is distinct from that of the multimeric enzyme, indicating that it may play a different role in starch metabolism.

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Published date: 1 January 2003

Identifiers

Local EPrints ID: 414030
URI: http://eprints.soton.ac.uk/id/eprint/414030
ISSN: 1040-4651
PURE UUID: 3c105ba8-4a43-4e0c-866f-3d22e9e53ae4
ORCID for Alexandra Mant: ORCID iD orcid.org/0000-0001-7169-209X

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Date deposited: 12 Sep 2017 16:32
Last modified: 07 Oct 2020 01:50

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Contributors

Author: Hasnain Hussain
Author: Alexandra Mant ORCID iD
Author: Robert Seale
Author: Sam Zeeman
Author: Edward Hinchliffe
Author: Anne Edwards
Author: Christopher Hylton
Author: Stephen Bornemann
Author: Alison M. Smith
Author: Cathie Martin
Author: Regla Bustos

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