Subcellular Localization of the Starch Degradative and Biosynthetic Enzymes of Spinach Leaves

Okita, Thomas W.; Greenberg, Elaine; Kuhn, David N.; Preiss, Jack

doi:10.1104/pp.64.2.187

Cited by 137 publications

(90 citation statements)

References 28 publications

(48 reference statements)

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“…Although AGP is in the chloroplasts of spinach (Spinacia oleracea) leaves (Okita et al, 1979) and in the amyloplast of potato tubers (Kim et al, 1989), recent protein Villand and Kleczkowski, 1994), genetic (Cao et al, 1995;Shannon et al, 1996), and cell fractionation studies (Denyer et al, 1996;Thorbjornsen et al, 1996b) provide strong arguments for a cytosolic localization of AGP activity in cereal endosperms. This localization is consistent with immunocytological studies in maize endosperm (Brangeon et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

Maize Genes Encoding the Small Subunit of ADP- Glucose Pyrophosphorylase

et al. 2001

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Plant ADP-glucose pyrophosphorylase (AGP) is a heterotetrameric enzyme composed of two large and two small subunits. Here, we report the structures of the maize (Zea mays) genes encoding AGP small subunits of leaf and endosperm. Excluding exon 1, protein-encoding sequences of the two genes are nearly identical. Exon 1 coding sequences, however, possess no similarity. Introns are placed in identical positions and exhibit obvious sequence similarity. Size differences are primarily due to insertions and duplications, hallmarks of transposable element visitation. Comparison of the maize genes with other plant AGP small subunit genes leads to a number of noteworthy inferences concerning the evolution of these genes. The small subunit gene can be divided into two modules. One module, encompassing all coding information except that derived from exon 1, displays striking similarity among all genes. It is surprising that members from eudicots form one group, whereas those from cereals form a second group. This implies that the duplications giving rise to family members occurred at least twice and after the separation of eudicots and monocot cereals. One intron within this module may have had a transposon origin. A different evolutionary history is suggested for exon 1. These sequences define three distinct groups, two of which come from cereal seeds. This distinction likely has functional significance because cereal endosperm AGPs are cytosolic, whereas all other forms appear to be plastid localized. Finally, whereas barley (Hordeum vulgare) reportedly employs only one gene to encode the small subunit of the seed and leaf, maize utilizes the two genes described here.The formation of ADP-Glc from Glc-1-phosphate and ATP with the release of pyrophosphate is considered the first committed step in the starch biosynthetic pathway. This key, rate-limiting reaction is catalyzed by the enzyme ADP-Glc pyrophosphorylase (AGP; EC 2.7.7.27). AGP isoforms occur in organisms and tissues ranging from Escherichia coli to the potato (Solanum tuberosum) tuber and the maize (Zea mays) endosperm (for review, see Preiss and

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Section: Discussionmentioning

confidence: 99%

Maize Genes Encoding the Small Subunit of ADP- Glucose Pyrophosphorylase

et al. 2001

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“…ADP-glucose pyrophosphorylase (ADGase) and UDP-glucose pyrophosphorylase were assayed using the coupled enzyme method described by OBrien (1976) with a pyrophosphate detection kit (Sigma). Amylase and starch phosphorylase activities were measured as described by Okita et al (1979).…”

Section: Enzyme Assaysmentioning

confidence: 99%

Monogenic Recessive Mutations Causing Both Late Floral Initiation and Excess Starch Accumulation in Arabidopsis.

et al. 1995

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A recessive Arabidopsis mutation, carbohydrate accumulation mutantl (caml), which maps to position 22.8 on chromosome 3, was identified by screening leaves of ethyl methanesulfonate-mutagenized M2 plants stained with iodine for altered starch content. lncreased starch content in leaves of the c a m l mutant was observed at the onset of flowering. This mutant also had a delayed floral initiation phenotype with more rosette leaves than the parenta1 line. In addition, activities of several enzymes associated with starch metabolism were altered in the c a m l mutant. The late-flowering mutant gigantea (gi) also manifested an elevated starch leve1 in leaves. However, not all late-flowering mutants had increased leaf starch content. Double mutants c a m l a d g l (for AJP-glucose pyrophosphorylase), c a m l pgm (for -phosphoglucomutase), and g i p g m had no observable starch in leaves but showed the late-flowering phenotype, demonstrating tThat the elevated starch content is not the cause of late floral initiation. The pleiotropic effects of c a m l and gi suggest that they may play regulatory roles in starch metabolism and floral initiation. These data suggest that starch accumulation and floral initiation may share a common regulatory pathway.

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“…Bacterial isoforms are homotetramers, whereas two distinct subunits make up the a 2 b 2 heterotetrameric plant enzymes. AGPase is located in the plastids of spinach (Spinacia oleracea) leaves (Okita et al, 1979) and potato (Solanum tuberosum) tubers (Kim et al, 1989); however, assorted studies identified a cytoplasmic location for endosperm AGPases (Giroux and Hannah, 1994;Villand and Kleczkowski;, Cao et al, 1995Denyer et al, 1996;Shannon et al, 1996;Thorbjornsen et al, 1996;Brangeon et al, 1997;Beckles et al, 2001). …”

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confidence: 99%

Characterization of an Autonomously Activated Plant ADP-Glucose Pyrophosphorylase

et al. 2008

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ADP-glucose pyrophosphorylase (AGPase) catalyzes the rate-limiting step in starch biosynthesis in plants and changes in its catalytic and/or allosteric properties can lead to increased starch production. Recently, a maize (Zea mays)/potato (Solanum tuberosum) small subunit mosaic, MP ], containing the first 198 amino acids of the small subunit of the maize endosperm enzyme and the last 277 amino acids from the potato tuber enzyme, was expressed with the maize endosperm large subunit and was reported to have favorable kinetic and allosteric properties. Here, we show that this mosaic, in the absence of activator, performs like a wild-type AGPase that is partially activated with 3-phosphoglyceric acid (3-PGA). In the presence of 3-PGA, enzyme properties of Mos(1-198)/SH2 are quite similar to those of the wild-type maize enzyme. In the absence of 3-PGA, however, the mosaic enzyme exhibits greater activity, higher affinity for the substrates, and partial inactivation by inorganic phosphate. The Mos(1-198)/SH2 enzyme is also more stable to heat inactivation. The different properties of this protein were mapped using various mosaics containing smaller portions of the potato small subunit. Enhanced heat stability of Mos(1-198) was shown to originate from five potato-derived amino acids between 322 and 377. These amino acids were shown previously to be important in small subunit/large subunit interactions. These five potato-derived amino acids plus other potato-derived amino acids distributed throughout the carboxyl-terminal portion of the protein are required for the enhanced catalytic and allosteric properties exhibited by Mos(1-198)/SH2.

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Subcellular Localization of the Starch Degradative and Biosynthetic Enzymes of Spinach Leaves

Cited by 137 publications

References 28 publications

Maize Genes Encoding the Small Subunit of ADP- Glucose Pyrophosphorylase

Maize Genes Encoding the Small Subunit of ADP- Glucose Pyrophosphorylase

Monogenic Recessive Mutations Causing Both Late Floral Initiation and Excess Starch Accumulation in Arabidopsis.

Characterization of an Autonomously Activated Plant ADP-Glucose Pyrophosphorylase

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