Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.1.14 (SPS)
 813 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The presence of sucrose synthetase and sucrose phosphate synthetase has been demonstrated in two species of green algae: Chlorella vulgaris and Scenedesmus obliquus. Partial purification from crude extracts allowed the determination of the kinetic constants of algae enzymes. They are very similar to the ones reported for enzymes from higher plants.
Mol Cell Biochem 1977 Jul 05
PMID:Sucrose metabolism in green algae. I. The presence of sucrose synthetase and sucrose phosphate synthetase. 1 67

A cDNA clone encoding a sucrose-phosphate synthase from sugar beet (BvSPS 1) has been isolated by screening a tap root-specific cDNA library using a heterologous SPS cDNA from spinach. The 3635 bp sugar beet cDNA codes for a 1045 amino acid polypeptide with a predicted molecular mass of 118 kDa. The deduced amino acid sequence of sugar beet SPS shows homologies with SPS from maize (71% identity) and spinach (77% identity). Genomic Southern blot analysis suggests that BvSPS 1 is a low-copy-number gene. RNA blot analysis of sink and source leaves, root and tap root tissue shows that SPS 1 is expressed in an organ-specific manner, being predominantly active in tap root. Incubation of detached leaves of sugar beet in light in glucose-containing media leads to an accumulation of the SPS transcript, while sucrose feeding reduces the steady-state level of the mRNA.
Mol Gen Genet 1995 May 20
PMID:Cloning and expression analysis of sucrose-phosphate synthase from sugar beet (Beta vulgaris L.). 777 61

The C57BL/10 SPS/sps mouse mutant are audiogenic seizure-susceptible. The enzymatic activities of glutamate decarboxylase (GAD), GABA aminotransferase (GABA-T), alanine aminotransferase (ALA-T), aspartate aminotransferase (ASP-T), and glutamate dehydrogenase (GDH) of whole brain supernatant are significantly reduced in these epileptic mice. GABA uptake is decreased in cortex, midbrain, and pons medulla. Previous studies showed the presence of two sodium-dependent GLU uptake systems in normal (SPS/SP) mice. Glutamate Umax by System 1 is significantly decreased in these mice, whereas the Umax value for System 2 is significantly increased in the epileptic mice.
Mol Neurobiol
PMID:Altered GABAergic and glutamatergic transmission in audiogenic seizure-susceptible mice. 788 3

The possible presence of a sucrose-phosphate synthase (SPS) activating/stabilizing factor (SAF) presumably lost during SPS purification was investigated. Rice leaf protein extracts were chromatographed in a DEAE-Sephacel column. SPS activity of previously purified rice enzyme was enhanced to different extent by aliquots of fractions from such column. The activating capacity could not be replaced by albumin, but was nullified by EDTA. When the fractions were boiled or treated with TCA, the activating capacity disappeared suggesting its proteinaceous nature. The presence of 10 microM okadaic acid had no effect on the stimulatory action of SAF on SPS denying the possibility to SAF to be a SPS-phosphatase. Although it overlaps somehow with sucrose synthase (SS) in DEAE-Sephacel fractions, the activating protein factor and SS eluted separately during Sephadex G-200 chromatography. The activating ability was saturable at a fixed SPS concentration and was able to enhance SPS activity from other plant sources. Simultaneous studies on the activities of SPS and sucrose-phosphate phosphatase (SPP), closely linked to SPS, allowed us to suggest that SAF could be SPP. The presence of SAF/SPP did not alter the affinity of SPS for its substrates but helped to reverse the Pi inhibition at low Fru-6-P concentrations. We conclude that SPS may possibly interact with SPP, contributing to a more effective sucrose synthesis.
Cell Mol Biol (Noisy-le-grand) 1996 Jul
PMID:Activation of sucrose-phosphate synthase by a protein factor/sucrose-phosphate phosphatase. 883 97

Light dependent modulation of sucrose-phosphate synthase activity (SPS; EC 2.4.1.14) was studied in a tree species, namely Prosopis juliflora. In this paper we demonstrate that cycloheximide, an inhibitor of cytoplasmic protein synthesis, when fed to detached leaves of P. juliflora through transpiration stream in the dark or in light completely prevents in vivo light activation of Vlim and Vmax activities of SPS. In case of spinach, however, cycloheximide feeding affects only Vlim activity while Vmax activity remained unchanged. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplast has no effect on the light activation of SPS in Prosopis. The treatment with cycloheximide showed slight reduction in the rate of O2 evolution indicating that cycloheximide had very little effect on overall photosynthesis. These results indicate that short term protein turnover of the SPS protein and some other essential component(s) (e.g., a putative protein that modifies SPS activity) is one of the primary steps in a complex and unique regulatory cascade effecting the reversible light activation of SPS.
Biochem Mol Biol Int 1997 Oct
PMID:Sucrose-phosphate synthase in tree species: light/dark regulation involves a component of protein turnover in Prosopis juliflora (SW DC). 935 Mar 50

Early during fruit ripening in kiwifruit (Actinidia deliciosa var. deliciosa [A. Chev.], C.F. Liang and A.R. Ferguson cv. Hayward), starch is broken down to sucrose and hexose sugars. Concomitantly, sucrose-phosphate synthase (SPS, EC 2.3.1.14) activity measured with saturating substrate increased, suggesting that SPS is induced in response to a higher requirement for sucrose synthesis. A 2584 bp long partial cDNA clone encoding SPS was isolated from ripening kiwifruit. cDNA fragments encoding the 5' end were isolated by PCR, and sequencing revealed at least four closely related (> 96% identity) mRNAs expressed early in kiwifruit ripening. Southern hybridisations in a diploid relative of kiwifruit, Actinidia chinensis (Planch.) var. chinensis, were consistent with the presence of a small gene family. Western analysis indicated a 125 kDa SPS protein present in all tissues of A. chitensis at all stages of development. Steady-state levels of SPS mRNA in A. chinensis increased near fruit maturity as net starch degradation began on the vine, and increased again during ethylene treatment of fruit after harvest. After removal from ethylene SPS transcript levels decreased, only to increase again as fruit moved into the climacteric and starch breakdown was completed. Exposure to low temperatures also caused an increase in SPS transcript level. These results indicate that SPS mRNA increases in kiwifruit in response to the presence of new substrate sourced from starch degradation, in response to ethylene and in response to low temperature.
Plant Mol Biol 1998 Apr
PMID:Sucrose-phosphate synthase steady-state mRNA increases in ripening kiwifruit. 952 Feb 77

Sucrose-phosphate synthase (SPS, EC 2.4.1.14) biochemical properties and peptide composition have been analyzed in rice leaf seedlings. SPS was purified using DEAE-Sephacel chromatography, gel filtration on Sepharose 6B and anion exchange chromatography on Mono Q. At this stage two enzyme forms (SPS-I and -II) were separated. SPS-II was purified 90-fold; however, SPS-I presented a lower specific activity regarding the previous purification step and an unstable activity. Both enzyme forms had similar apparent Km values for Fru-6P but the SPS-I Km for UDP-Glc was ca. 10-fold higher than the SPS-II one. In addition, they differentiate in the capacity of being modulated by Glc-6-P and Pi: while SPS-II activity was inhibited by Pi and activated by Glc-6-P, SPS-I was not affected by either effectors. A native molecular mass of ca. 420 kDa was found by gel filtration. In SPS expression analysis using leaf rice and wheat germ SPS antibodies, a 116 kDa polypeptide was revealed in rice leaf extracts and no polypeptide was immunoactive in rice roots.
Cell Mol Biol (Noisy-le-grand) 1998 May
PMID:Studies on sucrose-phosphate synthase from rice leaves. 962 Apr 36

Sucrose is one of several low-molecular-weight compounds that cyanobacteria accumulate in response to osmotic stress and which are believed to act as osmoprotectants. The genome of the cyanobacterium Synechocystis sp. PCC 6803 contains a 2163 bp open reading frame (ORF) that shows similarity to genes from higher plants encoding sucrose-phosphate synthase (SPS), the enzyme responsible for sucrose synthesis. The deduced amino acid sequence shows 35-39% identity with known higher-plant SPS sequences. The putative Synechocystis sps gene was cloned from genomic DNA by PCR amplification and expressed as a His6-tagged amino-terminal fusion protein in Escherichia coli. The expressed protein was purified and shown to be a functional SPS enzyme, confirming the identity of the ORF, which is the first sps gene to be cloned from a prokaryotic organism. The Synechocystis SPS has a molecular mass of 81.5 kDa, which is smaller than the typical higher-plant SPS subunit (117-119 kDa), and lacks the phosphorylation site motifs associated with light- and osmotic stress-induced regulation of SPS in higher plants. The enzyme has Km values for UDPG1c and Fru6P of 2.9 mM and 0.22 mM, respectively, with a Vmax of 17 micromol per minute per mg protein and a pH optimum of 8.5. Unlike the higher-plant enzyme, ADPG1c, CDPG1c and GDPG1c can substitute for UDPG1c as the glucosyl donor with Km values of 2.5, 7.2 and 1.8 mM, respectively. The enzyme is activated by Mg2+ but not by G1c6P, and is only weakly inhibited by inorganic phosphate. The purified protein was used to raise a high-titre antiserum, which recognises a low-abundance 81 kDa protein in Synechocystis sp. PCC 6803 extracts. There was no apparent increase in expression of the 81 kDa protein when the cells were exposed to moderate salt stress, and SPS activity was very low in extracts from both unstressed and salt-stressed cells. These results and the lack of evidence for sucrose accumulation in Synechocystis sp. PCC6803 lead to the conclusion that expression of the sps gene plays no obvious role in adaptation to osmotic stress in this species.
Plant Mol Biol 1999 May
PMID:Cloning and expression of a prokaryotic sucrose-phosphate synthase gene from the cyanobacterium Synechocystis sp. PCC 6803. 1041 8

Sucrose (Suc) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Suc synthesis and 'demand' for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Suc degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskeleton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.
Crit Rev Biochem Mol Biol 2000
PMID:Regulation of sucrose metabolism in higher plants: localization and regulation of activity of key enzymes. 1100 2

The primary target for light-chilling stress in chilling-sensitive cucumber leaves is the chloroplast Cu,Zn-Superoxide dismutase, followed by subsequent inactivation of the photosystem (PS) I by reactive oxygen species (ROS). To test this hypothesis, two rice cultivars that were different in their ecological origins (a chilling-resistant Stejaree 45 and a chilling-sensitive Milyang 23) were evaluated with respect to photosynthetic properties, the ROS scavenging system, and expression of genes that are involved in sucrose synthesis and allocation upon the light-chilling stress. As expected, when the leaves were exposed to various low temperatures with illumination (150 micromol m(-2)s(-1)) for 6 h, the leaf photosynthesis of Milyang 23 decreased faster than that of Stejaree 45. The light-chilling induced differential photoinhibition of photosynthesis between the two cultivars was caused by the photoin-activation of PSII but not of PSI, since the potential quantum yield of PSII followed a similar trend to the changes in photosynthetic rates. The activities of the two chloroplastic antioxidant enzymes (superoxide dismutase and ascorbate peroxidase) that are known to be sensitive to oxidative stress were barely affected by the light-chilling treatments. Among various genes in sucrose metabolism (such as cytosolic FBPase, SPS, SUT, SuSy, and AGPase), the transcript levels of SuSy in Milyang 23 were significantly decreased by light-chilling stress compared to that of Stejaree 45. Based on these results, we propose that PSII, not PSI, is the sensitive site for light-chilling stress in chilling-sensitive rice. The extent of PSII photoinhibition depends on its capacity for the photochemical utilization of light.
Mol Cells 2002 Jun 30
PMID:Differential susceptibility of photosynthesis to light-chilling stress in rice (Oryza sativa l.) depends on the capacity for photochemical dissipation of light. 1213 82


1 2 3 4 Next >>