Description
In enzymology, a leucine dehydrogenase (EC 1.4.1.9) is an enzyme that catalyzes the chemical reaction: L-leucine + H2O + NAD+ ↔ 4-methyl-2-oxopentanoate + NH3 + NADH + H+. The 3 substrates of this enzyme are L-leucine, H2O, and NAD+, whereas its 4 products are 4-methyl-2-oxopentanoate, NH3, NADH, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH2 group of donors with NAD+ or NADP+ as acceptor. This enzyme participates in valine, leucine and isoleucine degradation and valine, leucine and isoleucine biosynthesis.
Abbr
LeuDH, Native (Bacillus stearothermophilus)
Source
Bacillus stearothermophilus
Applications
The enzyme is useful for determination of L-leucine, L-valine or L-isoleucine.
Enzyme Commission Number
EC 1.4.1.9
Contaminants
(as LeuDH activity = 100 %)
NADH oxidase: < 0.01 %;
Lactate dehydrogenase: < 0.01 %.
Molecular Weight
ca. 300,000; Subunit molecular weight : ca. 49,000.
Michaelis Constant
(125mM Sodium phosphate buffer, pH 10.5, at 30 °C)
L-Leucine: 3.4 mM;
NAD+: 0.3 mM.
Specificity
L-Leucine: 100 %;
L-Valine : 86 %;
L-Isoleucine: 73 %.
Unit Definition
One unit of activity is defined as the amount of LeuDH that forms 1 μmol of NADH per minute at 30 °C
Thermal stability
No detectable decrease in activity up to 60 °C.
Storage
Stable at -20 °C for at least one year.
Synonyms
EC 1.4.1.9; Leucine dehydrogenase; L-leucine: NAD+ oxidoreductase (deaminating); L-leucine dehydrogenase; L-leucine: NAD+ oxidoreductase (deaminating); LeuDH
Specific Activity
more than 40 U/mg protein
Reaction
L-Leucine + NAD+ + H2O ←→ α-Ketoisocaproate+ NH4+ +NADH
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