▎ 摘　　要

NOVELTY - Preparing graphene-modified electrochemical biosensor comprises cleaning and pre-treating gold electrode, fixing the nucleotide sequence on the gold electrode and using mercaptohexanol to block the portion of the nucleotide sequence that is not bound to the gold electrode to obtain a gold electrode with the nucleotide sequence fixed, immobilizing obtained gold electrode with nucleotide sequence is treated with methylation-sensitive restriction endonuclease and extended with terminal transferase, and immersing in buffer solution containing graphene oxide to fully function to obtain a graphene-modified electrochemical biosensor. USE - The graphene-modified electrochemical biosensor is useful in detection of methyltransferase in the range of 0.7-12 U/ml. ADVANTAGE - The sensor system is stable, simple to operate, and can quickly and easily determine the methyltransferase in the test solution to qualitatively. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) graphene-modified electrochemical biosensor prepared by above method; and (2) use of graphene-modified electrochemical biosensor in detection of methyltransferase, when methyltransferase is present in the buffer system to be detected, it can catalyze the 5'-CCGG-3' methylation of the CpG sequence in the nucleotide sequence immobilized on the gold electrode, as a result, methylation-sensitive restriction endonucleases cannot perform catalysis and subsequent reactions, the detected electrode impedance modified by methyltransferase will be significantly greater than the electrode impedance of the graphene-modified electrochemical biosensor, so as to achieve the detection purpose.