The present invention discloses a method for preparing L-glufosinate ammonium by biological enzymatic de-racemization, a glufosinate ammonium dehydrogenase mutant and a use thereof. The method for preparing L-glufosinate ammonium by biological enzymatic de-racemization includes catalyzing D,L-glufosinate ammonium as a raw material by a multi-enzyme catalysis system to obtain L-glufosinate ammonium. The enzyme catalysis system includes D-amino acid oxidase for catalyzing D-glufosinate ammonium in the D,L-glufosinate ammonium to 2-carbonyl-4-[hydroxy(methyl)phosphonyl]butanoic acid, and a glufosinate ammonium dehydrogenase mutant for catalytically reducing 2-carbonyl-4-[hydroxy(methyl)phosphonyl]butanoic acid to L-glufosinate ammonium. The glufosinate ammonium dehydrogenase mutant is obtained by mutation of glufosinate-ammonium dehydrogenase in wild fungi Thiopseudomonas denitrificans at a mutation site of V377S. The glufosinate ammonium dehydrogenase mutant in the present invention has better catalytic efficiency. When racemic D, L-glufosinate ammonium is used as a substrate for a catalytic reaction, the conversion rate is much higher than the conversion rate of a wild-type enzyme, and the yield of 2-carbonyl-4-[hydroxy(methyl)phosphonyl]butanoic acid (PPO for short) is also greatly improved.

The present invention refers to a modified D-amino acid oxidase (DAAO). In particular, the modified DAAO of the present invention has the activity of catalyzing the oxidation of D-glufosinate into PPO. Further, the modified DAAO of the present invention has increased activity of catalyzing the oxidation of D-glufosinate into PPO and/or increased stability as compared to SEQ ID NO: 4. The present invention also refers to the polynucleotide encoding the modified DAAO of the present invention, the vector and host cell expressing the modified DAAO of the present invention, and the method of producing L-glufosinate with the modified DAAO and host cell of the present invention.

Disclosed in the present disclosure is a method for preparing (S)-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid and derivatives thereof, comprising: taking a racemate of a compound represented by Formula (I) or a racemate of a salt of the compound represented by Formula (I) as a substrate, and making a R-isomer of the compound represented by Formula (I) in the substrate react under the catalysis of oxidative dehydrogenase to generate imino acid represented by formula (II); and converting the imino acid represented by Formula (II) into an S-isomer of the compound represented by Formula (I) in the presence of pipecolic acid reductase and a coenzyme capable of supplying hydrogen anions. The present disclosure is featured by mild reaction condition, strong stereoselectivity, high reaction efficiency, high conversion rate, etc.

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Provided is a D-amino acid oxidative enzyme mutant. The sequence of the mutant comprises a sequence by mutating the 54.sup.th amino acid residue N, the 58.sup.th amino acid residue F, the 211.sup.th amino acid residue C, and the 213.sup.th amino acid residue M of the sequence shown in SEQ ID NO:1 or the sequence having at least 76% identity with SEQ ID NO:1. The D-amino acid oxidative enzyme mutant has a higher enzyme activity, enzyme activity stability and/or ammonium resistance than a mild D-amino acid oxidative enzyme mutant. Also provided is an application of the D-amino acid oxidative enzyme mutant in preparing 2-oxo-4-(hydroxymethylphosphinyl)butyric acid.

The present invention refers to a modified D-amino acid oxidase (DAAO). In particular, the modified DAAO of the present invention has the activity of catalyzing the oxidation of D-glufosinate into PPO. Further, the modified DAAO of the present invention has increased activity of catalyzing the oxidation of D-glufosinate into PPO and/or increased stability as compared to SEQ ID NO: 4. The present invention also refers to the polynucleotide encoding the modified DAAO of the present invention, the vector and host cell expressing the modified DAAO of the present invention, and the method of producing L-glufosinate with the modified DAAO and host cell of the present invention.

Methods for preparing crystalline L-glufosinate ammonium monohydrate are disclosed. The methods include forming a mixture comprising water, a water-miscible organic solvent, ammonium hydroxide, and a glufosinate starting material containing L-glufosinate ammonium and D-glufosinate ammonium. L-Glufosinate ammonium monohydrate is crystallized and separated from the mixture, providing L-glufosinate ammonium monohydrate Form B. Compositions and methods employing the crystalline L-glufosinate ammonium monohydrate are also described.

Provided is a D-amino acid oxidative enzyme mutant. The sequence of the mutant comprises a sequence by mutating the 54.sup.th amino acid residue N, the 58.sup.th amino acid residue F, the 211.sup.th amino acid residue C, and the 213.sup.th amino acid residue M of the sequence shown in SEQ ID NO:1 or the sequence having at least 76% identity with SEQ ID NO:1. The D-amino acid oxidative enzyme mutant has a higher enzyme activity, enzyme activity stability and/or ammonium resistance than a mild D-amino acid oxidative enzyme mutant. Also provided is an application of the D-amino acid oxidative enzyme mutant in preparing 2-oxo-4-(hydroxymethylphosphinyl)butyric acid.

A method for asymmetrically preparing L-phosphinothricin by oxidation-reduction reaction through biological multienzyme coupling, where D,L-phosphinothricin as a raw material is catalyzed by an enzyme catalysis system to obtain L-phosphinothricin, wherein the enzyme catalysis system comprises a D-amino acid oxidase mutant for catalyzing D-phosphinothricin in D,L-phosphinothricin into 2-carbonyl-4-[hydroxy(methyl)phosphono]butyric acid and a transaminase for catalytic reduction of the 2-carbonyl-4-[hydroxy(methyl) phosphono]butyric acid into L-phosphinothricin; the D-amino acid oxidase mutant is obtained by mutation of D-amino acid oxidase in wild strain Rhodotorula taiwanensis at one of the following four sites: (1) M213S; (2) M213S-N54V-F58E; (3) M213S-N54V-F58E-D207A; (4) M213S-N54V-F58E-D207A-S60T. According to the present invention, the D-amino acid oxidase mutant provides better catalytic efficiency, and when racemic D,L-phosphinothricin is used as a substrate for catalytic reaction, the conversion rate is much higher than that of the wild type enzyme, and the PPO yield is also greatly improved.

Embodiments of the present disclosure relate to a D-amino acid oxidase mutant and application in preparing L-glufosinate thereof. The D-amino acid oxidase mutant has an amino acid substitution at at least one of position 62 and position 226 of an amino acid sequence of the D-amino acid oxidase mutant when compared to an amino acid sequence of a D-amino acid oxidase as set forth in SEQ ID NO. 1, the position 62 and position 226 being defined with reference to SEQ ID NO. 1, and the amino acid sequence of the D-amino acid oxidase mutant having at least 90% identity to SEQ ID NO. 1.

Embodiments of the present disclosure relate to a D-amino acid oxidase mutant and application in preparing L-glufosinate thereof. The D-amino acid oxidase mutant has an amino acid substitution at at least one of position 62 and position 226 of an amino acid sequence of the D-amino acid oxidase mutant when compared to an amino acid sequence of a D-amino acid oxidase as set forth in SEQ ID NO. 1, the position 62 and position 226 being defined with reference to SEQ ID NO. 1, and the amino acid sequence of the D-amino acid oxidase mutant having at least 90% identity to SEQ ID NO. 1.