The invention discloses high-
stereoselectivity methionine adenosyltransferase as well as a preparation method and application thereof. The preparation method comprises the following steps: extracting a
genome of
streptomyces xinghaiensis; by taking a
genome as
a DNA (
Deoxyribose Nucleic Acid) template and adopting a PCR (
Polymerase Chain Reaction) amplification technology, obtaining a
gene sequence of
methionine adenosyltransferase in the
streptomyces xinghaiensis, namely a metK target fragment; carrying out double
enzyme digestion on the metK target fragment and an
expression vector pET-32a (+), and then connecting to construct a recombinant
plasmid; transforming the recombinant
plasmid into competent cells of
escherichia coli BL21 by adopting a thermal
activation method, and carrying out inducible expression by virtue of
isopropyl-beta-D-thiogalactoside, so as to obtain SxMAT. According to the invention, high-
stereoselectivity methionine adenosyltransferase is subjected to denaturation and renaturation later to obtain high-purity SxMAT, the SxMAT is good in stability when the temperature is 25-55 DEG C and the pH value is 8-10.5, the optical purity (ee) of the product is higher than 90%, the yield is 80%, and the in-vitro double-
enzyme cascade reaction is constructed by combining the SxMAT and the fluorinase, so that the understanding of people on a fluorination pathway in
streptomyces is facilitated, and the application of fluorinated natural products is derived.