An Escherichia coli K-12 tktA tktB mutant deficient in transketolase activity requires pyridoxine (vitamin B6) as well as the aromatic amino acids and vitamins for growth

Zhao, Genshi; Winkler, Malcolm E.

doi:10.1128/jb.176.19.6134-6138.1994

Cited by 89 publications

(83 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This likely catalyzes the aforementioned reactions Sasajima, 1984, 1986), since other previously characterized E. coli transketolases, A and B, are not involved in deoxy-xylulose synthesis (Zhao and Winkler, 1994). Thus, CapTKT2 could be designated as a deoxyxylulose synthase, as shown for E. coli (Sprenger et al, 1997).…”

Section: The Role Of Transketolase In Generating Carbon-carbon Condenmentioning

confidence: 99%

Dedicated Roles of Plastid Transketolases during the Early Onset of Isoprenoid Biogenesis in Pepper Fruits1

et al. 1998

View full text Add to dashboard Cite

Isopentenyl diphosphate (IPP), which is produced from mevalonic acid or other nonmevalonic substrates, is the universal precursor of isoprenoids in nature. Despite the presence of several isoprenoid compounds in plastids, enzymes of the mevalonate pathway leading to IPP formation have never been isolated or identified to our knowledge. We now describe the characterization of two pepper (Capsicum annuum L.) cDNAs, CapTKT1 and CapTKT2, that encode transketolases having distinct and dedicated specificities. CapTKT1 is primarily involved in plastidial pentose phosphate and glycolytic cycle integration, whereas CapTKT2 initiates the synthesis of isoprenoids in plastids via the nonmevalonic acid pathway. From pyruvate and glyceraldehyde-3-phosphate, CapTKT2 catalyzes the formation of 1-deoxy-xylulose-5-phosphate, the IPP precursor. CapTKT1 is almost constitutively expressed during the chloroplast-to-chromoplast transition, whereas CapTKT2 is overexpressed during this period, probably to furnish the IPP necessary for increased carotenoid biosynthesis. Because deoxy-xylulose phosphate is shared by the plastid pathways of isoprenoid, thiamine (vitamin B 1 ), and pyridoxine (vitamin B 6 ) biosynthesis, our results may explain why albino phenotypes usually occur in thiaminedeficient plants.Because of the combined activities of mevalonatesynthesizing and -activating enzymes, IPP is known as the universal isoprenoid building block. How IPP is synthesized and channeled into plastid isoprenoids to support the production of carotenoids, chlorophylls, prenylquinones, and diterpenes is largely unknown. Two hypotheses have been proposed. One is that plastids operate autonomously, synthesizing plastid isoprenoids directly from carbon dioxide or from plastid glycolytic intermediates such as pyruvate (Goodwin, 1971;Moore and Shephard, 1978; Heintze et al., 1990 Heintze et al., , 1994McCaskill and Croteau, 1995). However, the mechanism of carbon flow via a pyruvate intermediate is unknown for plants. A second hypothesis is that IPP is transported from the cytosol (Kleinig, 1989), which is based on the finding that hydroxymethylglutaryl CoA reductase and mevalonate-activating enzymes are absent in plastids (Gray, 1987). This view is reinforced by the fact that mevilonin, a specific inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, drastically inhibits cytosolic sterol biosynthesis at moderate concentrations but does not affect isoprenoid synthesis in plastids (Bach and Lichtenthaler, 1983). This led to consideration of an alternative IPP-generation system. In fact, such a pathway is known for prokaryotes, in which IPP is formed via deoxy-xylulose phosphate rather than by mevalonate (Rohmer et al., 1993) in a transketolation reaction between pyruvate and glyceraldehyde-3-phosphate . In vivo precursor labeling indicates that a similar pathway operates for the synthesis of ginkgolides (Schwarz, 1994) and plastid isoprenoids (Schwender et al., 1996; Arigoni et al., 1997;Lichtenthaler et al., 1997aLichtenthaler et al., , 1997b.In t...

show abstract

Section: The Role Of Transketolase In Generating Carbon-carbon Condenmentioning

confidence: 99%

Dedicated Roles of Plastid Transketolases during the Early Onset of Isoprenoid Biogenesis in Pepper Fruits1

et al. 1998

View full text Add to dashboard Cite

show abstract

“…SerA, and the fact that 4-hydroxy-L-threonine is struc turally related to serine, it was suggested that the pdxB gene product is erythronate-4-phosphate dehydroge nase (24). It was also revealed that serC mutant, tktA tktB double mutant and gapA epd double mutant require B6, suggesting that these genes are involved in B6 biosynthesis (23,25,26).…”

Section: Evidence From Tracer Experiments In the 1960-80smentioning

confidence: 99%

“…Biochemical approaches were also applied to prove the biosynthetic pathway proposed by Winkler (25) (Fig. 3).…”

Section: Evidence From Tracer Experiments In the 1960-80smentioning

confidence: 99%

Recent Progress of Vitamin B6 Biosynthesis

Sakai

Kita

Tani

2004

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

View full text Add to dashboard Cite

SummaryThis review is the current summary of vitamin B6 (B6) biosynthesis in Escheri chic coli and other microorganisms. The de novo biosynthesis of B6 has been studied exten sively for last three decades. However, the de novo biosynthesis of B6 still remains unclear in spite of its simple structure. For the first two decades, B6 biosynthesis had been mainly stud ied with E. coil using genetic, nutritional, and isotopic labeling experiments. According to these studies, some compounds including glycolaldehyde were identified as the precursor. During the last decade, gene manipulate techniques were rapidly developed, and complete genome sequences of some microorganisms became available. Using these new tools, valu able information has been provided. The complete DNA sequence of pdx genes and other genes, which are possibly involved in B6 biosynthesis, were shown. The roles of some genes and precursors were proposed. Besides E. coli, B6 biosynthesis in other microorganisms has been also studied. In some microorganisms, snz/sno was reported to be involved in B6 bio synthesis. Intriguingly, these genes show no similarity to any of the E. coil pdx genes, and are not found in E. coil. Microorganisms having snz/sno gene homologues lack homologues to pdxA/pdxJ genes, whereas those with homologues to pdxA/pdxJ lack snz/sno gene homo logues. Therefore, it is most likely that there are at least two kinds of B6 biosynthetic path ways in microorganisms. These studies provided important clues of B6 biosynthesis, but the entire picture of the B6 biosynthetic pathway remains unclear.

show abstract

“…This compound is thought to be der ved from 3-hydroxy-4-O-phosphoryl-2-oxobutyrate by transamination. The transaminase is encoded by pdxC(serC), a ~ene believed to be involved in both serine and 4-hydroxy-Lt lreonine biosynthesis, or its phosphorylated derivatives [3]. l~,lutants lacking a functional allele of the gene fail to synthes ze both serine and vitamin B6 [4~6].…”

Section: Introductionmentioning

confidence: 99%

“…Whereas Dempsey and c ~workers have detected phosphoserine aminotransferase ac-! vity with 3-O-phospho-e-serine as the substrate [5], evidence t)r 3-hydroxy-4-O-phosphoryl-2-oxobutyrate and 4-O-phos-1 horyl-e-threonine as intermediates in vitamin B6 formation i circumstantial [3,7]. In both transamination reactions, the ~ mino group of glutamic acid is transferred to the acceptor c~-xoacids, yielding the corresponding amino acids and a-oxolutarate ( Fig.…”

Section: Introductionmentioning

confidence: 99%

4‐O‐Phosphoryl‐l‐threonine, a substrate of the pdxC(serC) gene product involved in vitamin B₆ biosynthesis

et al. 1996

View full text Add to dashboard Cite

The Escherichia coli pdxC(serC) gene codes for a transaminase (EC 2.6.1.52). The gene is involved in both pyridoxine (vitamin B6) and serine biosynthesis and was overexpressed as a MalEIPdxC(SerC) fusion protein. The fusion protein was purified by aff'mity chromatography on an amylose resin and hydrolyzed in the presence of protease factor Xa. Both the fusion protein and the PdxC(SerC) protein were characteri~ed (KM value, turnover number, optimum pH). Both enzymes used 4-O-phosphoryl-L-threonine rather than 4-hydroxy-L-threonine as a substrate indicating that the phosphorylated rather than the non-phosphorylated amino acid is involved in pyridoxine biosynthesis. Pyridoxal phosphate was shown to be the cofactor for both enzymes and therefore seems to be involved in its own biosynthesis.

show abstract

An Escherichia coli K-12 tktA tktB mutant deficient in transketolase activity requires pyridoxine (vitamin B6) as well as the aromatic amino acids and vitamins for growth

Cited by 89 publications

References 19 publications

Dedicated Roles of Plastid Transketolases during the Early Onset of Isoprenoid Biogenesis in Pepper Fruits1

Dedicated Roles of Plastid Transketolases during the Early Onset of Isoprenoid Biogenesis in Pepper Fruits1

Recent Progress of Vitamin B6 Biosynthesis

4‐O‐Phosphoryl‐l‐threonine, a substrate of the pdxC(serC) gene product involved in vitamin B₆ biosynthesis

Contact Info

Product

Resources

About

An Escherichia coli K-12 tktA tktB mutant deficient in transketolase activity requires pyridoxine (vitamin B6) as well as the aromatic amino acids and vitamins for growth

Cited by 89 publications

References 19 publications

Dedicated Roles of Plastid Transketolases during the Early Onset of Isoprenoid Biogenesis in Pepper Fruits1

Dedicated Roles of Plastid Transketolases during the Early Onset of Isoprenoid Biogenesis in Pepper Fruits1

Recent Progress of Vitamin B6 Biosynthesis

4‐O‐Phosphoryl‐l‐threonine, a substrate of the pdxC(serC) gene product involved in vitamin B6 biosynthesis

Contact Info

Product

Resources

About

4‐O‐Phosphoryl‐l‐threonine, a substrate of the pdxC(serC) gene product involved in vitamin B₆ biosynthesis