1. A 2-0-sulfation enzyme mutant, having a substitution of a leucine residue at
position 321 with a basic amino acid residue in any one amino acid sequence of:
(a) the amino acid sequence of SEQ ID NO: 2;
(b) an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence of SEQ ID NO: 2; or
(c) an amino acid sequence having 90% or more identity to the amino acid sequence of SEQ ID NO: 2; or
(d) the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2;
(e) an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2; or
(f) an amino acid sequence having 90% or more identity to the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2; and
having a 2-O-sulfate transfer activity.
2. The 2-O-sulfation enzyme mutant according to claim 1, wherein the basic amino acid residue is an arginine residue or a lysine residue.
3. A method of producing a modified heparosan compound in which a hydroxyl group at 2-position of a hexuronic acid residue is sulfated, comprising converting a heparosan compound into a modified heparosan compound in which a hydroxyl group at

2-position of a hexuronic acid residue is sulfated in the presence of a 2-O-sulfation enzyme mutant,
wherein the 2-O-sulfation enzyme mutant is a 2-O-sulfation enzyme mutant having a substitution of a leucine residue at position 321 with a basic amino acid residue in any one amino acid sequence of:
(a) the amino acid sequence of SEQ ID NO: 2;
(b) an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence of SEQ ID NO: 2; or
(c) an amino acid sequence having 90% or more identity to the amino acid sequence of SEQ ID NO: 2; or
(d) the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2;
(e) an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2; or
(f) an amino acid sequence having 90% or more identity to the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2; and
having a 2-O-sulfate transfer activity.
4. The method according to claim 3, wherein the heparosan compound is N-sulfated heparosan, N-sulfated epimerized heparosan, N-sulfated depolymerized heparosan, or N-sulfated epimerized depolymerized heparosan.
5. The method according to claim 3 or 4, wherein the heparosan compound in

which a hydroxyl group at 2-position of a hexuronic acid residue is sulfated is produced in the presence of a transformed microorganism which produces the 2-O-sulfation enzyme mutant, or an extract thereof.
6. The method according to claim 5, wherein the transformed microorganism is a bacterium belonging to the genus Escherichia.
7. The method according to claim 6, wherein the bacterium belonging to the genus Escherichia is Escherichia coll
8. A 3-O-sulfation enzyme mutant, wherein in any one amino acid sequence of:
(a') the amino acid sequence of SEQ ID NO: 8;
(b') an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence of SEQ ID NO: 8; or
(c') an amino acid sequence having 90% or more identity to the amino acid sequence ofSEQIDNO:8;or
(d') the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8;
(e') an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8; or
(f) an amino acid sequence having 90% or more identity to the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8;
(i) a methionine residue at position 77 is substituted with a lysine residue;

(ii) a tryptophan residue at position 96 is substituted with a phenylalanine residue;
(iii) a proline residue at position 125 is substituted with an alanine residue;
(iv) a valine residue at position 164 is substituted with an isoleucine residue;
(v) an asparagine residue at position 167 is substituted with a histidine residue;
(vi) a lysine residue at position 171 is substituted with a glutamine residues; or
(vii) a tyrosine residue at position 259 is substituted with a phenylalanine residue; and
wherein the 3-O-sulfation enzyme mutant has a 3-O-sulfate transfer activity.
9. A method of producing a modified heparosan compound in which a hydroxyl
group at 3-position of an a-D-glucosamine residue is sulfated, comprising converting a heparosan compound into a modified heparosan compound in which a hydroxyl group at 3-position of an a-D-glucosamine residue is sulfated in the presence of a 3-O-sulfation enzyme mutant,
wherein the 3-O-sulfation enzyme mutant is a 3-O-sulfation enzyme mutant, in which in any one amino acid sequence of:
(a') the amino acid sequence of SEQ ID NO: 8;
(b') an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence of SEQ ID NO: 8; or
(c') an amino acid sequence having 90% or more identity to the amino acid sequence of SEQ ID NO: 8; or
(d') the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8;
(e') an amino acid sequence comprising one or several amino acid substitutions,

deletions, insertions, or additions in the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8; or
(f) an amino acid sequence having 90% or more identity to the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8;
(i) a methionine residue at position 77 is substituted with a lysine residue;
(ii) a tryptophan residue at position 96 is substituted with a phenylalanine residue;
(iii) a proline residue at position 125 is substituted with an alanine residue;
(iv) a valine residue at position 164 is substituted with an isoleucine residue;
(v) an asparagine residue at position 167 is substituted with a histidine residue;
(vi) a lysine residue at position 171 is substituted with a glutamine residues; or
(vii) a tyrosine residue at position 259 is substituted with a phenylalanine residue; and
wherein the 3-O-sulfation enzyme mutant has a 3-O-sulfate transfer activity.
10. The method according to claim 9, wherein the heparosan compound is N-sulfated 6-O-sulfated heparosan, N-sulfated 6-O-sulfated epimerized heparosan, N-sulfated 2-O-sulfated 6-O-sulfated heparosan, N-sulfated 2-O-sulfated 6-O-sulfated epimerized depolymerized heparosan, N-sulfated 6-O-sulfated depolymerized heparosan, N-sulfated 6-O-sulfated epimerized depolymerized heparosan, N-sulfated 2-O-sulfated 6-O-sulfated depolymerized heparosan, or N-sulfated 2-O-sulfated 6-O-sulfated epimerized depolymerized heparosan.
11. The method according to claim 9 or 10, wherein the modified heparosan

compound in which a hydroxyl group at 3-position of an cc-D-glucosamine residue is sulfated is produced in the presence of a transformed microorganism which produces the 3-O-sulfation enzyme mutant, or an extract thereof.
12. The method according to claim 11, wherein the transformed microorganism is a bacterium belonging to the genus Escherichia.
13. The method according to claim 12, wherein the bacterium belonging to the genus Escherichia is Escherichia col.
14. A method of producing a heparan sulfate, comprising subjecting heparosan to a treatment comprising (1) N-deacetylation of cc-D-glucosamine residue, (2) depolymerization, (3) N-sulfation of cc-D-glucosamine residue, (4) C5-epimerization of hexuronic acid residue, (5) 2-O-sulfation of hexuronic acid residue, (6) 6-O-sulfation of a-D-glucosamme residue, and (7) 3-O-sulfation of cc-D-glucosamme residue to produce a heparan sulfate,
wherein:
(I) the 2-O-sulfation of the hexuronic acid residue is performed in the presence of a 2-O-sulfation enzyme mutant having a substitution of a leucine residue at position 321 with a basic amino acid residue in any one amino acid sequence of:
(a) the amino acid sequence of SEQ ID NO: 2;
(b) an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence of SEQ ID NO: 2; or
(c) an amino acid sequence having 90% or more identity to the amino acid sequence of SEQ ID NO: 2; or

(d) the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2;
(e) an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2; or
(f) an amino acid sequence having 90% or more identity to the amino acid sequence consisting of amino acid residues at positions 69 to 356 in the amino acid sequence of SEQ ID NO: 2; and
having a 2-O-sulfate transfer activity; or
(II) the 3-O-sulfation of the a-D-glucosamine residue is performed in the presence of a 3-O-sulfation enzyme mutant, in which in any one amino acid sequence of:
(a') the amino acid sequence of SEQ ID NO: 8;
(b') an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence of SEQ ID NO: 8; or
(c') an amino acid sequence having 90% or more identity to the amino acid sequence of SEQ ID NO: 8; or
(d') the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8;
(e') an amino acid sequence comprising one or several amino acid substitutions, deletions, insertions, or additions in the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8; or
(f) an amino acid sequence having 90% or more identity to the amino acid sequence consisting of amino acid residues at positions 48 to 311 in the amino acid sequence of SEQ ID NO: 8;
(i) a methionine residue at position 77 is substituted with a lysine residue;

(ii) a tryptophan residue at position 96 is substituted with a phenylalanine residue;
(iii) a proline residue at position 125 is substituted with an alanine residue;
(iv) a valine residue at position 164 is substituted with an isoleucine residue;
(v) an asparagine residue at position 167 is substituted with a histidine residue;
(vi) a lysine residue at position 171 is substituted with a glutamine residues; or
(vii) a tyrosine residue at position 259 is substituted with a phenylalanine residue; and
wherein the 3-O-sulfation enzyme mutant has a 3-O-sulfate transfer activity.