Conjugate of a tissue non-specific alkaline phosphatase and dextran, process for its production and use thereof

1. A conjugate comprising an unglycosylated tissue non-specific alkaline phosphatase (tns-AP) comprising amino acids 18-504 of SEQ ID NO:4 and dextran.

2. The conjugate of claim 1 , wherein the tns-AP is obtained by recombinant expression of a nucleic acid coding for tns-AP in a prokaryotic cell.

3. The conjugate of claim 1 or 2 , wherein the dextran has an average molecular weigh of 10-500 kDa.

4. A method for producing a conjugate comprising reacting an unglycosylated tns-AP comprising amino acids 18-504 of SEQ ID NO:4 with activated dextran by incubation in an aqueous solution, stopping the reaction and isolating the conjugate from the solution.

5. The method of claim 4 , wherein the tns-AP is obtained by recombinant expression of a nucleic acid coding for the tns-AP in a prokaryotic cell.

6. The method of claim 4 or 5 , wherein the dextran has an average molecular weight of 10-500 kDa.

7. The method of claim 4 or 5 , wherein the activated dextran is activated with CDAP or CNBr.

8. The method of claim 4 or 5 , wherein the unglycosylated tns-AP and the activated dextran are used for the said reaction in a ratio of 1:2 to 1:500.

9. A method for quantitating alkaline phosphatase activity comprising:

a) obtaining a serum sample from a patient;

b) determining alkaline phosphatase activity in the serum sample;

c) comparing the alkaline phosphatase activity in the serum sample to a standard comprising a conjugate comprising an unglycosylated tissue non-specific alkaline phosphatase comprising amino acids 18-504 of SEQ ID NO:4 and dextran; and

d) quantitating alkaline phosphatase activity in the serum sample based on the comparison.