Method for detecting l-serine based on Escherichia coli cysteine desulfurase

A method for detecting L-serine in an unknown sample with Escherichia coli cysteine desulfurase, comprising the steps of:

• reacting the unknown sample with Escherichia coli cysteine desulfurase in vitro;
• observing a color of a resulting reaction solution to determine whether a stable red substance is produced after the reaction;
• observing a color depth of the red substance with naked eyes;
• and
• qualitatively determining the presence or absence of the L-serine in the unknown sample and an L-serine content of the unknown sample;
• wherein if the red substance is present, the L-serine content in the unknown sample is quantitatively determined by a process comprising:
• measuring absorbances of L-serine standard solutions after reacting the solutions with Escherichia coli cysteine desulfurase to produce the red substance;
• constructing a standard curve based on the absorbances of the L-serine standard solutions;
• measuring an absorbance of the unknown sample;
• and
• substituting the absorbance of the unknown sample into an equation of the standard curve to quantitatively obtain the L-serine content in the unknown sample;
• wherein the reacting of the L-serine standard solutions and the unknown sample with Escherichia coli cysteine desulfurase occurs for a reaction time of 60-180 min;
• wherein the absorbances of the L-serine standard solutions and the unknown sample are measured at a wavelength of 528 nm;
• and
• wherein the Escherichia coli cysteine desulfurase has the amino acid sequence of SEQ ID NO:
• 1.