Izumoring

Granström, Tom; Takata, Goro; Tokuda, Masaaki; Izumori, Ken

doi:10.1016/s1389-1723(04)70173-5

Cited by 302 publications

(41 citation statements)

References 36 publications

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“…Xylulose is phosphorylated to xylulose-5-phosphate, an intermediate metabolite of the pentose phosphate pathway and thus a substrate for cellular metabolism. However, xylulose is not naturally available in significant amounts outside of living cells [18, 19] and can therefore be viewed as an ‘unfamiliar’ or ‘novel’ carbon source for which yeast did not undergo evolutionary adaptation. Inter-strain diversity in growth rate and ethanol production was significantly higher during growth on xylulose than that observed during growth on other ‘familiar’ carbon sources such as glucose and galactose.…”

Section: Introductionmentioning

confidence: 99%

Rapid evolutionary adaptation to growth on an ‘unfamiliar’ carbon source

et al. 2016

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BackgroundCells constantly adapt to changes in their environment. When environment shifts between conditions that were previously encountered during the course of evolution, evolutionary-programmed responses are possible. Cells, however, may also encounter a new environment to which a novel response is required. To characterize the first steps in adaptation to a novel condition, we studied budding yeast growth on xylulose, a sugar that is very rarely found in the wild.ResultsWe previously reported that growth on xylulose induces the expression of amino acid biosynthesis genes in multiple natural yeast isolates. This induction occurs despite the presence of amino acids in the growth medium and is a unique response to xylulose, not triggered by naturally available carbon sources. Propagating these strains for ~300 generations on xylulose significantly improved their growth rate. Notably, the most significant change in gene expression was the loss of amino acid biosynthesis gene induction. Furthermore, the reduction in amino-acid biosynthesis gene expression on xylulose was tightly correlated with the improvement in growth rate, suggesting that internal depletion of amino-acids presented a major bottleneck limiting growth in xylulose.ConclusionsWe discuss the possible implications of our results for explaining how cells maintain the balance between supply and demand of amino acids during growth in evolutionary ‘familiar’ vs. ‘novel’ conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3010-x) contains supplementary material, which is available to authorized users.

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Section: Introductionmentioning

confidence: 99%

Rapid evolutionary adaptation to growth on an ‘unfamiliar’ carbon source

et al. 2016

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“…Because of the very small amounts of d -psicose in natural products, few studies have examined d -psicose metabolism in animals. Recently, we developed a new method for producing d -psicose enzymatically on a large scale [2], making it possible to conduct such studies. We have since demonstrated that d -psicose is a sweet carbohydrate that provides no energy to growing rats [3–5] and that it causes little toxic effect in rats [6–7].…”

Section: Introductionmentioning

confidence: 99%

Retraction: D-Psicose Inhibits Intestinal ^|^alpha;-Glucosidase and Suppresses the Glycemic Response after Ingestion of Carbohydrates in Rats

Matsuo

Izumori

2009

J. Clin. Biochem. Nutr.

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d-psicose is one of the rare sugars present in small quantities in commercial carbohydrates and agricultural products. In this study, we investigated the effects of d-psicose on the activities of α-amylases and α-glucosidases in vitro, and evaluated the effects of d-psicose on the in vivo postprandial glycemic response using rats. In the in vitro study, d-psicose potently inhibited the intestinal sucrase and maltase, however, slightly inhibited the intestinal and salivary α-amylase activities. Male Wistar rats (6 months old) were administrated 2 g/kg of sucrose, maltose or soluble starch together with 0.2 g/kg of d-psicose or d-fructose. The d-psicose significantly inhibited the increment of plasma glucose concentration induced by sucrose or maltose. The starch-induced glycemic response tended to be suppressed by d-psicose, however the suppression was not significant. These results suggest that d-psicose inhibits intestinal sucrase and maltase activities and suppresses the plasma glucose increase the normally occurs after sucrose and maltose ingestion. Thus, d-psicose may be useful in preventing postprandial hyperglycemia in diabetic patients when foods containing sucrose and maltose are ingested.

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“…As such, we sought to investigate the possibility that GalE might mediate the conversion of non-nucleic acid-activated glucose to galactose because this enzymatic process has potential application in the commercial manufacture of rare saccharides from naturally abundant glucose [14]. Although directed evolution has become a powerful tool to improve enzymes for commercial purposes, the availability of an original template would provide a greater chance of acquiring desirable characteristics [15].…”

Section: Introductionmentioning

confidence: 99%

Novel Activity of UDP-Galactose-4-Epimerase for Free Monosaccharide and Activity Improvement by Active Site-Saturation Mutagenesis

Kim

Kang

Kim

2010

Appl Biochem Biotechnol

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Uridine diphosphogalactose-4-epimerase (UDP-galactose-4-epimerase, GalE, EC 5.1.3.2) mediates the 4-epimerization of nucleic acid-activated galactose into UDP-glucose. To date, no enzyme is known to mediate 4-epimerization of free monosaccharide substrates. To determine the potential activity of GalE for free monosaccharide, Escherichia coli GalE was expressed and purified using Ni-affinity chromatography, and its ability to mediate 4-epimerization of a variety of free keto- and aldohexoses was assessed. Purified GalE was found to possess 4-epimerization activity for free galactose, glucose, fructose, tagatose, psicose, and sorbose at 0.47, 0.31, 2.82, 9.67, 15.44, and 2.08 nmol/mg protein per minute, respectively. No 4-epimerization activity was found for allose, gulose, altrose, idose, mannose, and talose. The kinetic parameters of 4-epimerization reactions were K (m) = 26.4 mM and k (cat) = 0.0155 min(-1) for D-galactose and K (m) = 237 mM and k (cat) = 0.327 min(-1) for D-tagatose. The 4-epimerization of tagatose, a reaction of commercial interest, was enhanced twofold (19.79 nmol/mg protein per minute) when asparagine was exchanged with serine at position 179. The novel activity of GalE for free monosaccharide may be beneficial for the production of rare sugars using cheap natural resources. Potential strategies for developing enhanced GalE with increased 4-epimerization activity are discussed in the context of the above findings and an analysis of a 3D structural model.

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Izumoring

Cited by 302 publications

References 36 publications

Rapid evolutionary adaptation to growth on an ‘unfamiliar’ carbon source

Rapid evolutionary adaptation to growth on an ‘unfamiliar’ carbon source

Retraction: D-Psicose Inhibits Intestinal ^|^alpha;-Glucosidase and Suppresses the Glycemic Response after Ingestion of Carbohydrates in Rats

Novel Activity of UDP-Galactose-4-Epimerase for Free Monosaccharide and Activity Improvement by Active Site-Saturation Mutagenesis

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