[Technical Field]
The present disclosure relates to an O-phosphoserine export protein, and a method for
producing O-phosphoserine, cysteine, and cysteine derivatives using the same.
5 [Background Art]
L-Cysteine, an amino acid which has an important role in sulfur metabolism in all living
organisms, is used not only in the synthesis of biological proteins such as hair keratin, etc.,
glutathione, biotin, methionine, and other sulfur-containing metabolites, but also as a precursor
for biosynthesis of coenzyme A.
10 Methods of producing L-cysteine using microorganisms known in the art include: 1) a
method of biologically converting D,L-2-amino-2-thiazoline-4-carboxylic acid (D,L-ATC) into
L-cysteine using microorganisms, 2) a method of producing L-cysteine by direct fermentation
using E. coli (EP 0885962 B; Wada M and Takagi H, Appl. Microbiol. Biochem., 73:48–54,
2006), and 3) a method of producing O-phosphoserine (hereinafter, “OPS”) by fermentation
15 using microorganisms, and then converting O-phosphoserine into L-cysteine by reacting
O-phosphoserine with a sulfide under the catalytic action of O-phosphoserine sulfhydrylase
(hereinafter, “OPSS”) (European Patent No. 2444481).
In particular, in order to produce cysteine by the method 3) in high yield, OPS, the
precursor, should be produced in an excess amount.
20 Under such circumstances, the present inventors have made extensive efforts to identify a
suitable export factor that can smoothly export O-phosphoserine produced in an OPS-producing
strain outside of cells and to increase the OPS production. As a result, they have discovered a
novel OPS export protein, thereby completing the present disclosure.
25 [Disclosure]
[Technical Problem]
The present inventors have made extensive efforts to identify appropriate exporting
factors capable of smoothly exporting O-phosphoserine outside of cells and to increase the
production of OPS, and as a result, they have found a novel OPS exporting protein, thereby
30 completing the present disclosure.
[Technical Solution]
It is one object of the present disclosure to provide a recombinant microorganism for
3
producing O-phosphoserine in which the activity of mdtH protein is enhanced compared to its
endogenous activity.
It is another object of the present disclosure to provide a method for producing
O-phosphoserine using the recombinant microorganism for producing O-phosphoserine of the
5 present disclosure.
It is still another object of the present disclosure to provide a method for producing
cysteine or derivatives thereof using the recombinant microorganism for producing
O-phosphoserine of the present disclosure.
10 [Advantageous Effects]
When O-phosphoserine is produced using the recombinant microorganism for producing
O-phosphoserine in which the activity of mdtH protein is enhanced compared to its endogenous
activity, it can lead to high-yield production of O-phosphoserine compared to using an existing
non-modified strain.

We Claim:
1. A recombinant microorganism for producing O-phosphoserine in which the activity of
mdtH protein is enhanced compared to its endogenous activity.
5
2. The microorganism of claim 1, in which the O-phosphoserine exporting activity is
enhanced compared to its endogenous activity.
3. The microorganism of claim 1, wherein the mdtH protein comprises an amino acid
10 sequence of SEQ ID NO: 1, or an amino acid sequence having at least 95% identity with
SEQ ID NO: 1, while having the O-phosphoserine exporting activity.
4. The microorganism of claim 1, in which the activity of phosphoserine phosphatase (SerB)
is further weakened compared to its endogenous activity.
15
5. The microorganism of claim 1, in which the activity of any one of phosphoglycerate
dehydrogenase (SerA), phosphoserine aminotransferase (SerC), or a combination thereof is
further enhanced compared to its endogenous activity.
20 6. The microorganism of claim 1, wherein the recombinant microorganism belongs to the
genus Escherichia.
7. A method for producing O-phosphoserine, comprising culturing a recombinant
microorganism for producing O-phosphoserine in which the activity of mdtH protein is
25 enhanced compared to its endogenous activity, in a medium.
8. The method of claim 7, wherein the method further comprises recovering
O-phosphoserine in the cultured medium or the microorganism.
30 9. A method for producing cysteine or derivatives thereof, comprising:
a) producing O-phosphoserine or a medium containing O-phosphoserine by culturing a
recombinant microorganism for producing O-phosphoserine in which the activity of
mdtH protein is enhanced compared to its endogenous activity, in a medium; and
34
b) reacting the O-phosphoserine or the medium containing the same produced in Step a)
with a sulfide, in the presence of O-phosphoserine sulfhydrylase (OPSS) or a
microorganism containing the same.
5 10. The method of claim 9, wherein the method for producing cysteine derivatives further
comprises converting cysteine produced in Step b) into cysteine derivatives.
11. The method of claim 9, wherein the sulfide is at least one selected from the group
consisting of Na2S, NaSH, (NH4)2S, H2S, and Na2S2O3.
10
12. Use of a recombinant microorganism for the production of O-phosphoserine for
producing O-phosphoserine, cysteine, or a derivative of cysteine, in which the activity of a
mdtH protein is enhanced compared to its endogenous activity.
15 13. Use of a mdtH protein for exporting O-phosphoserine from a microorganism.