Monamycin C

Nanomaterials-based bioinspired enzyme mimics are gaining increased attention as alternatives to biocatalysts. Herein, we report synthesizing oxygen-terminated few-layered titanium-based MXene nanosheets (OFL-Ti-MN). OFL-Ti-MN possesses horseradish peroxidase (HRP) activity in catalyzing the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2), which turns the solution color bluish-green. The solution color fades quickly when kanamycin (KAN) is added to this system. This reaction indicates that KAN can prevent color change in the OFL-Ti-MN/TMB-H2O2 system. Based on this strategy, we developed an OFL-Ti-MN-based colorimetric sensor to detect and quantify KAN. The sensor exhibited a dynamic range from 15.28 nM to 46.14 μM and a calculated limit of detection (LOD) of 15.28 nM. From the insight gained from the peroxidase-mimic property of OFL-Ti-MN, we proposed a mechanism for the inhibition effect of KAN on peroxidase and peroxidase-mimic enzymes. The proposed mechanism can potentially help elucidate the reasons for the antibacterial function of KAN and its side effects in humans.

Kanamycin A is the major 2-deoxystreptamine (2DOS)-containing aminoglycoside antibiotic produced by Streptomyces kanamyceticus. The 2DOS moiety is linked with 6-amino-6-deoxy-d-glucose (6ADG) at O-4 and 3-amino-3-deoxy-d-glucose at O-6. Because the 6ADG moiety is derived from d-glucosamine (GlcN), deamination at C-2 and introduction of C-6-NH2 are required in the biosynthesis. A dehydrogenase, KanQ, and an aminotransferase, KanB, are presumed to be responsible for the introduction of C-6-NH2 , although the substrates have not been identified. Here, we examined the substrate specificity of KanQ to better understand the biosynthetic pathway. It was found that KanQ oxidized kanamycin C more efficiently than the 3''-deamino derivative. Furthermore, the substrate specificity of an oxygenase, KanJ, that is responsible for deamination at C-2 of the GlcN moiety was examined, and the crystal structure of KanJ was determined. It was found that C-6-NH2 is important for substrate recognition by KanJ. Thus, the modification of the GlcN moiety occurs after pseudo-trisaccharide formation, followed by the introduction of C-6-NH2 by KanQ/KanB and deamination at C-2 by KanJ.

A highly sensitive kanamycin electrochemiluminescence (ECL) switch sensor was constructed. A signal element consisting of ordered mesoporous carbon loaded with indium oxide nanoparticles/carbon quantum dots (OMC/In2O3/C-dots) was assembled on the surface of a gold electrode. Then, a molecularly imprinted polymer (MIP) was prepared on the modified electrode surface using kanamycin as the template molecule and o-aminophenol as the functional monomer. After kanamycin elution, the prepared sensor retained specific kanamycin recognition sites. OMC/In2O3 effectively amplified the ECL signal of the C-dots, thereby enhancing the detection sensitivity, whereas kanamycin quenched the signal. Therefore, the imprinted sites acted as a switch, providing a new method for detecting kanamycin. Under the optimal experimental conditions, the concentration of kanamycin was proportional to the degree of ECL quenching within a linear range of 5-4500 × 10-12 mol L-1 at 0.8 V (vs. Ag/AgCl electrode electrode), and the detection limit was 5.8 × 10-13 mol L-1. When applied to the detection of kanamycin in actual samples, such as chicken, duck, pork, and milk, the recovery for spiked samples was in the range 92.7-110%.