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Literature summary for 5.1.3.5 extracted from

  • Zhang, Q.; Shirley, N.J.; Burton, R.A.; Lahnstein, J.; Hrmova, M.; Fincher, G.B.
    The genetics, transcriptional profiles, and catalytic properties of UDP-alpha-D-xylose 4-epimerases from barley (2010), Plant Physiol., 153, 555-568.
    View publication on PubMedView publication on EuropePMC

Activating Compound

Activating Compound Comment Organism Structure
dithiothreitol
-
Hordeum vulgare
dithiothreitol 150% activity at 2 mM Hordeum vulgare

Cloned(Commentary)

Cloned (Comment) Organism
isoform UXE1 is expressed in Pichia pastoris Hordeum vulgare

Inhibitors

Inhibitors Comment Organism Structure
additional information UMP and EDTA do not inhibit the activity of the recombinant isoform UXE1 Hordeum vulgare
UDP 15% residual activity at 2 mM Hordeum vulgare
UTP 54% residual activity at 2 mM Hordeum vulgare

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
1.4
-
UDP-beta-L-arabinopyranose pH 7.0, at 25°C Hordeum vulgare
1.8
-
UDP-alpha-D-xylopyranose pH 7.0, at 25°C Hordeum vulgare

Metals/Ions

Metals/Ions Comment Organism Structure
additional information Mg2+ does not stimulate the activity of the recombinant isoform UXE1. Addition of NADH or NAD+ has no significant effect on activity Hordeum vulgare

Molecular Weight [Da]

Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
45000
-
isoform UXE3, calculated from amino acid sequence Hordeum vulgare
47000
-
isoform UXE1, calculated from amino acid sequence Hordeum vulgare

Organism

Organism UniProt Comment Textmining
Hordeum vulgare Q2LC81 isoform UXE3
-
Hordeum vulgare Q2LC82 isoform UXE2
-
Hordeum vulgare Q2LC83 isoform UXE1
-

Purification (Commentary)

Purification (Comment) Organism
Ni-NTA column chromatography Hordeum vulgare

Source Tissue

Source Tissue Comment Organism Textmining
endosperm
-
Hordeum vulgare
-

Storage Stability

Storage Stability Organism
4°C, purified enzyme, at least 1 week, little or no loss of activity Hordeum vulgare

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
additional information the purified recombinant isoform UXE1 does not catalyze the interconversion of UDP-glucose and UDP-galactose Hordeum vulgare ?
-
?
UDP-alpha-D-xylopyranose
-
Hordeum vulgare UDP-beta-L-arabinopyranose
-
r
UDP-beta-L-arabinopyranose
-
Hordeum vulgare UDP-alpha-D-xylopyranose
-
r

Synonyms

Synonyms Comment Organism
UDP-alpha-D-xylose 4-epimerase
-
Hordeum vulgare
UXE1 isoform Hordeum vulgare
UXE2 isoform Hordeum vulgare
UXE3 isoform Hordeum vulgare

Turnover Number [1/s]

Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
1.5
-
UDP-beta-L-arabinopyranose pH 7.0, at 25°C Hordeum vulgare
1.5
-
UDP-alpha-D-xylopyranose pH 7.0, at 25°C Hordeum vulgare

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
7
-
about pH 7.0 Hordeum vulgare

Cofactor

Cofactor Comment Organism Structure
NAD+
-
Hordeum vulgare
NAD+ each molecule of isoform UXE1 contains about one molecule of noncovalently bound NAD+ Hordeum vulgare

Expression

Organism Comment Expression
Hordeum vulgare isoform UXE2 transcript abundance is moderate during the syncytial stage of endosperm development (2-6 days after pollination) but decreases to undetectable levels beyond 6 days after pollination down
Hordeum vulgare in developing barley endosperm, isoform UXE3 mRNA levels peak at a time when UDP-alpha-D-xylopyranose synthase transcripts also reach a maximum and when arabinoxylan biosynthesis is initiated up
Hordeum vulgare in developing barley endosperm, isoforms UXE1 mRNA levels peak at a time when UDP-alpha-D-xylopyranose synthase transcripts also reach a maximum and when arabinoxylan biosynthesis is initiated. Transcript levels for the UXE1 gene are about 4fold higher at 9 days after pollination than in the syncytial and cellularization stages up

kcat/KM [mM/s]

kcat/KM Value [1/mMs-1] kcat/KM Value Maximum [1/mMs-1] Substrate Comment Organism Structure
0.9
-
UDP-alpha-D-xylopyranose pH 7.0, at 25°C Hordeum vulgare
1.1
-
UDP-beta-L-arabinopyranose pH 7.0, at 25°C Hordeum vulgare