Enzymatic properties and regulation of ZPU1, the maize pullulanase-type starch debranching enzyme

Wu, Chunyuan; Colleoni, Christophe; Myers, Alan M.; James, Martha G.

doi:10.1016/s0003-9861(02)00412-5

Cited by 38 publications

(25 citation statements)

References 41 publications

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“…Stephen et al 14 demonstrated that cysteine proteinases are stimulated by the thioredoxin system. Furthermore, and in contrast to our findings, Wu et al 18 did find that a combination of dithiothreitol and thioredoxin was able to stimulate LD activity in maize. We did not assess the combined impact of DTT and the thioredoxin system in the present work.…”

Section: Activation Of Ldcontrasting

confidence: 99%

Thioredoxin in Barley: Could It Have a Role in Releasing Limit Dextrinase in Brewery Mashes?

Heisner

Bamforth

2008

Journal of the Institute of Brewing

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There is not a strong correlation between the amount of thioredoxin in barley and the total protein content of the grain. The level of detectable thioredoxin decreases during germination, whereas the amount of limit dextrinase increases, for the most part in a bound form. Under no circumstances could a release of limit dextrinase in an active form be demonstrated through the agency of the thioredoxin system. By contrast the thiol agent dithiothreitol, especially in the presence of calcium, did promote the activation of limit dextrinase. Of most pronounced effect, however, was the lowering of pH. Three-fold higher limit dextrinase activity was achieved when the pH was lowered to 4.0

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Section: Activation Of Ldcontrasting

confidence: 99%

Thioredoxin in Barley: Could It Have a Role in Releasing Limit Dextrinase in Brewery Mashes?

Heisner

Bamforth

2008

Journal of the Institute of Brewing

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“…Accordingly, isoamylase-type DBE would not fully compensate for the loss of pullulanasetype DBE. In vitro studies of recombinant maize pullulanasetype DBE show clear differences in substrate preference compared with isoamylase-type DBE, with pullulanases generally preferring shorter chains (Rahman et al, 1998;Wu et al, 2002). This fact, along with the high degree of evolutionary conservation of both classes of DBEs, is consistent with the hypothesis that enzyme specificity is the reason that starch degradation is reduced in zpu1-204 mutants.…”

Section: Discussionsupporting

confidence: 71%

Mutational Analysis of the Pullulanase-Type Debranching Enzyme of Maize Indicates Multiple Functions in Starch Metabolism

et al. 2003

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Plants contain two types of ␣ (1 → 6) glucan hydrolase (starch-debranching enzyme [DBE]). Mutations that affect the pullulanase-type DBE have not been described, although defects in isoamylase-type DBE, known in many plant species, indicate a function in starch biosynthesis. We describe a null mutation of a pullulanase-type DBE gene, a Mutator insertion in maize Zpu1 . Plants homozygous for the zpu1-204 mutation are impaired in transient and storage starch degradation. Thus, hydrolytic activity of pullulanase-type DBE contributes to starch catabolism. Developing zpu1-204 endosperm accumulates branched maltooligosaccharides not found in the wild type and is deficient in linear maltooligosaccharides, indicating that the pullulanase-type DBE functions in glucan hydrolysis during kernel starch formation. Furthermore, in a background deficient in isoamylase-type DBE, zpu1-204 conditions a significant accumulation of phytoglycogen in the kernel that is not seen in the wild type. Therefore, pullulanase-type DBE partially compensates for the defect in isoamylase-type DBE, suggesting a function during starch synthesis as well as degradation.

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“…It is known that LDA and ISA3 preferentially remove short branches and have their highest activity on b-limit dextrins (Wu et al, 2002;Hussain et al, 2003;Delatte et al, 2006;Takashima et al, 2007). However, branching enzymes do not generate branches as short as d.p.…”

Section: The Functions Of Isa3 and Ldamentioning

confidence: 99%

Starch Granule Biosynthesis in Arabidopsis Is Abolished by Removal of All Debranching Enzymes but Restored by the Subsequent Removal of an Endoamylase

et al. 2008

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Several studies have suggested that debranching enzymes (DBEs) are involved in the biosynthesis of amylopectin, the major constituent of starch granules. Our systematic analysis of all DBE mutants of Arabidopsis thaliana demonstrates that when any DBE activity remains, starch granules are still synthesized, albeit with altered amylopectin structure. Quadruple mutants lacking all four DBE proteins (Isoamylase1 [ISA1], ISA2, and ISA3, and Limit-Dextrinase) are devoid of starch granules and instead accumulate highly branched glucans, distinct from amylopectin and from previously described phytoglycogen. A fraction of these glucans are present as discrete, insoluble, nanometer-scale particles, but the structure and properties of this material are radically altered compared with wild-type amylopectin. Superficially, these data support the hypothesis that debranching is required for amylopectin synthesis. However, our analyses show that soluble glucans in the quadruple DBE mutant are degraded by a-and b-amylases during periods of net accumulation, giving rise to maltose and branched malto-oligosaccharides. The additional loss of the chloroplastic a-amylase AMY3 partially reverts the phenotype of the quadruple DBE mutant, restoring starch granule biosynthesis. We propose that DBEs function in normal amylopectin synthesis by promoting amylopectin crystallization but conclude that they are not mandatory for starch granule synthesis.

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Enzymatic properties and regulation of ZPU1, the maize pullulanase-type starch debranching enzyme

Cited by 38 publications

References 41 publications

Thioredoxin in Barley: Could It Have a Role in Releasing Limit Dextrinase in Brewery Mashes?

Thioredoxin in Barley: Could It Have a Role in Releasing Limit Dextrinase in Brewery Mashes?

Mutational Analysis of the Pullulanase-Type Debranching Enzyme of Maize Indicates Multiple Functions in Starch Metabolism

Starch Granule Biosynthesis in Arabidopsis Is Abolished by Removal of All Debranching Enzymes but Restored by the Subsequent Removal of an Endoamylase

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