The development of simple, portable, inexpensive, and rapid analytical methods for detecting and monitoring toxic heavy metals are important for the safety and security of humans and their environment. Herein, we describe the application of phytochelatin (PC) synthase, which plays a critical role in heavy metal responses in higher plants and green algae, in a novel fluorescent sensing platform for cadmium (Cd). We first created surface-engineered yeast cells on which the PC synthase from Arabidopsis (AtPCS1) was displayed with retention of enzymatic activity. The general concept for the sensor is based on the Cd level-dependent synthesis of PC2 from glutathiones by AtPCS1-displaying yeast cells, followed by simple discriminative detection of PC2 via sensing of excimer fluorescence of thiol-labeling pyrene probes. The intensity of excimer fluorescence increased in the presence of Cd up to 1.0 μM in an approximately dose-dependent manner. This novel biosensor achieved a detection limit of as low as 0.2 μM (22.5 μg/L) for Cd. Although its use may be limited by the fact that Cu and Pb can induce cross-reaction, the proposed simple biosensor holds promise as a method useful for cost-effective screening of Cd contamination in environmental and food samples. The AtPCS1-displaying yeast cells also might be attractive tools for dissection of the catalytic mechanisms of PCS.
Gamma-glutamyl-cysteine (c-EC) is a precursor of glutathione (GSH) biosynthesis. We investigated whether it functions as a substrate for three intracellular and one extracellular GSH metabolic enzymes, which mediate the antioxidant defence function of GSH. Among them, glutathione peroxidase, glutathione S-transferase and c-glutamyl transferase (GGT) exhibited substrate specificity for c-EC, whereas glutathione reductase did not. The specificities of c-EC and its disulphide form to GGT were comparable to GSH and its oxidized form, GSSG respectively. These results indicate that they can supply GSH constituent amino acids, glutamate, cysteine and cystine through degradation by GGT. c-EC may contribute valuable antioxidant defence properties as a food and cosmetic additive.
We investigated whether it is possible to produce vinblastine by irradiation of blue light (B, 440 nm) and ultraviolet A light (UVA, 370 nm) to Catharanthus roseus for domestic production of vinblastine using an environmentally controlled room with artificial lighting, such as a plant factory. Catharanthus roseus plants were cultivated under red light (R, 660 nm) for 28 d and then were cultivated under 3 light quality treatments: UVA supplemented with R, B, or R for 7 d. At 3 d after treatments, vinblastine content in the leaves increased sharply under UVA supplemented with R compared with R alone. The vinblastine content under B was 1/6 of that under UVA supplemented with R. Vinblastine content increased as the UVA intensity was increased from 0 to 10 Wm 2 . UVA irradiation to the leaf discs made from the younger leaves raised the vinblastine content in the leaf discs more than those from the aged leaves. Therefore, UVA light should be irradiated to the young plants at early vegetable stage. For the domestic production of vinblastine, we proposed that the cultivation method of irradiating young plants with 10 Wm 2 UVA for more than 3 d.
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