Method of producing heterogeneous protein

1. A method of producing an antibody, comprising culturing an animal cell which expresses alanine aminotransferase and has a transferred DNA encoding the antibody and thereby allowing the animal cell to produce the antibody,

wherein the animal cell is a cell transformed with DNA encoding the alanine aminotransferase; and

wherein the alanine aminotransferase is any one of the following (a)-(c):

(a) a polypeptide having the amino acid sequence as shown in SEQ ID NO: 10;

(b) a polypeptide which has an amino acid sequence derived from the amino acid sequence as shown in SEQ ID NO: 10 by substitution, deletion, addition and/or insertion of 1-5 amino acid residues and yet has alanine aminotransferase activity; and

(c) a polypeptide having 99% or more amino acid sequence homology with the amino acid sequence as shown in SEQ ID NO: 10 and yet having alanine aminotransferase activity.

2. The method of claim 1 , wherein the animal cell further expresses a taurine transporter wherein the animal cell is a cell into which DNA encoding a taurine transporter has been transferred.

3. The method of claim 1 , wherein the cell is a Chinese hamster ovary cell.

4. A cultured cell transformed with DNA encoding a polypeptide having the amino acid sequence as shown in SEQ ID NO: 10 and a transferred DNA encoding a desired antibody.

5. A cultured cell transformed with DNA encoding a polypeptide having the amino acid sequence as shown in SEQ ID NO: 10 and DNA encoding a taurine transporter.

6. A method of producing a desired polypeptide, comprising culturing in an α-ketoglutarate-containing medium a cell transformed with DNA encoding alanine aminotransferase and which has a transferred DNA encoding the desired polypeptide and thereby allowing the cell to produce said desired polypeptide, wherein the alanine aminotransferase is any one of the following (a)-(c):

(a) a polypeptide having the amino acid sequence as shown in SEQ ID NO: 10;

(b) a polypeptide which has an amino acid sequence derived from the amino acid sequence as shown in SEQ ID NO: 10 by substitution, deletion, addition and/or insertion of 1-5 amino acid residues and yet has alanine aminotransferase activity; and

(c) a polypeptide having 99% or more amino acid sequence homology with the amino acid sequence as shown in SEQ ID NO: 10.

7. A method of producing an antibody, comprising culturing an animal cell which expresses alanine aminotransferase and has a transferred DNA encoding the antibody and thereby allowing the animal cell to produce the antibody,

wherein the animal cell is a cell transformed with exogenous DNA encoding the alanine aminotransferase; and

wherein the alanine aminotransferase is a hamster aminotransferase.

8. The method of claim 7 , wherein the animal cell further expresses a taurine transporter wherein the animal cell is a cell into which DNA encoding a taurine transporter has been transferred.

9. The method of claim 7 , wherein the cell is a Chinese hamster ovary cell.

10. A cultured cell transformed with exogenous DNA encoding a hamster alanine aminotransferase and a transferred DNA encoding a desired antibody.

11. The method of claim 1 or 7 , wherein the animal cell which further has a transferred DNA encoding a taurine transporter.

12. A cultured cell transformed with exogenous DNA encoding a hamster alanine aminotransferase and DNA encoding a taurine transporter.

13. A method of producing a desired polypeptide, comprising culturing in an α-ketoglutarate-containing medium a cell transformed with exogenous DNA encoding alanine aminotransferase and which has a transferred DNA encoding the desired polypeptide and thereby allowing the cell to produce said desired polypeptide, wherein the alanine aminotransferase is a hamster alanine aminotransferase.