Engineered aryl sulfate-dependent enzymes
The present invention provides several non-naturally occurring sulfotransferase enzymes that have been engineered to react with aryl sulfate compounds as sulfo group donors, instead of the natural substrate 3′-phosphoadenosine 5′-phosphosulfate (PAPS), and with heparosan-based polysaccharides, particularly heparan sulfate, as sulfo group acceptors. Each of the engineered sulfotransferase enzymes have a biological activity characterized by the position within the heparosan-based polysaccharide that receives the sulfo group, including glucosaminyl N-sulfotransferase activity, hexuronyl 2-O sulfotransferase activity, glucosaminyl 6-O sulfotransferase activity, or glucosaminyl 3-O sulfotransferase activity. Methods of using the engineered sulfotransferases to produce sulfated heparosan-based polysaccharides, including polysaccharides having anticoagulant activity, are also provided.
1. A method of enzymatically forming an N-,2-O,3-O,6-O-sulfated heparan sulfate (N,2O,3O,6O-HS) product in the absence of 3′-phosphoadenosine 5′-phosphosulfate (PAPS), the method comprising the following steps:
a. forming a reaction mixture comprising:
i. a sulfo group donor, the sulfo group donor consisting of an aryl sulfate compound;
ii. N-,2-O,6-O-sulfated heparan sulfate (N,2O,6O-HS); and
iii. a non-natural glucosaminyl 3-O sulfotransferase enzyme (3OST), engineered to have sulfotransferase activity with an aryl sulfate compound as a sulfo group donor and N,2O,6O-HS as a sulfo group acceptor;
b. binding the aryl sulfate compound within the enzyme active site; and
c. catalyzing the transfer of the sun group from the aryl sulfate compound to N,2O,6O-HS, thereby forming the N,2O,3O,6O-HS product.
2. The method of claim 1 , wherein the non-natural 3OST enzyme is a mutant of a natural 3OST enzyme within enzyme class EC 2.8.2.23, the natural 3OST enzyme having sulfotransferase activity with N,2O,6O-HS and a sulfo group donor, the sulfo group donor consisting of PAPS, to form an N,2O,6O-HS product, wherein:
a. the natural 3OST enzyme comprises the following conserved amino acid sequence motifs:
i. a conserved amino acid sequence motif having the amino acid sequence, SEQ ID NO: 265;
ii. a conserved amino acid sequence motif having the amino acid sequence, SEQ ID NO: 266; and
iii. a conserved amino acid sequence motif having the amino acid sequence, SEQ ID NO: 267; and
b. within the amino acid sequence of the non-natural 3OST enzyme,
i. amino acid sequence SEQ ID NO: 265 is mutated to SEQ ID NO: 268, and
ii. amino acid sequence SEQ ID NO: 266 is mutated to SEQ ID NO: 269.
3. The method of claim 2 , wherein within the amino acid sequence of the non-natural 3OST enzyme, amino acid sequence SEQ ID NO: 267 is mutated to SEQ ID NO: 270.
4. The method of claim 2 , wherein the non-natural 3OST enzyme comprises an amino acid sequence selected from the group consisting of the amino acid sequences of SEQ ID NO: 154, SEQ ID NO: 155, SEQ ID NO: 156, SEQ ID NO: 157, SEQ ID NO: 158 SEQ ID NO: 159, and SEQ ID NO: 160.
5. The method of claim 4 , wherein amino acid residues within SEQ ID NO: 154 having the designation, “Xaa,” are selected such that the non-natural 3OST enzyme has an amino acid sequence selected from the group consisting of the amino acid sequences of SEQ ID NO: 147, SEQ ID NO: 149, and SEQ ID NO: 151.
6. The method of claim 1 , wherein the aryl sulfate compound is selected from the group consisting of p-nitrophenyl sulfate (PNS) and 4-nitrocatechol sulfate (NCS).
7. The method of claim 1 , wherein the N,2O,3O,6O-HS product comprises a polysaccharide sequence motif having the structure of Formula I, below:
wherein X is either a sulfo group or an acetate group and Y is either a sulfo group or a hydroxyl group.
8. The method of claim 7 , wherein the N,2O,3O,6O-HS product has anticoagulant activity.
9. The method of claim 8 , wherein the N,2O,6O-HS is present within the reaction mixture as a polydisperse mixture of heparan sulfate polysaccharides, and the resulting N,2O,3O,6O-HS product has a weight average molecular weight, M w , of at least 1,000 Da.
10. The method of claim 9 , wherein the N,2O,3O,6O-HS product has molecular weight properties that are equivalent to the United States Pharmacopeia (USP) reference standard for heparin, CAS No: 9041-08-1.
11. The method of claim 10 , wherein the N,2O,3O,6O-HS product has an equivalent anticoagulant activity to USP heparin.