| 摘要 |
PURPOSE: Provided are a DNA encoding for a novel enzyme, namely levodione reductase, an expression vector comprising the DNA, a recombinant vector comprising the DNA, a microorganism into which the DNA has been introduced, and a method for producing (4R, 6R)-4-hydroxy-2,2,6-trimethylcyclohexanone (hereinafter referred to as actinol) from (6R)-2,2,6-trimethyl-1,4-cyclohexanedione (hereinafter referred to as levodione) using the microorganism. Actinol is a useful chiral building block of naturally occurring optically active compounds such as zeaxanthin. CONSTITUTION: The isolated DNA comprises a nucleotide sequence cording for the enzyme having levodione reductase activity with the following physico-chemical properties: 1) the levodione reductase catalyzes regio- and stereoselective reduction of levodione to actinol; 2) the relative molecular mass of the enzyme is estimated to be 142,000-155,000 +/- 10,000 Da consisting of four homologous subunits having a molecular mass of 36,000 +/- 5,000 Da; 3) the optimum temperature is 15-20 DEG C at pH 7.0 and the optimum pH is 7.5; and 4) the enzyme requires NAD or NADH as a cofactor and is highly activated by monovalent cations, such as K, Na, Cs, Rb and NH4. The DNA is characterized in that 1) the nucleotide sequence codes for enzyme having the amino acid sequence shown in SEQ ID No.: 1, or 2) the nucleotide sequence codes for a variant of the enzyme selected from (i) an allelic variant or (ii) an enzyme having one or more amino acid addition, insertion, deletion and/or substitution but having still the same type of enzymatic activity. |
