G-site residue S67 is involved in the fungicide-degrading activity of a tau class glutathione S-transferase from Carica papaya.

Thiram is a toxic fungicide extensively used for the management of pathogens in fruits. Although it is known that thiram degrades in plant tissues, the key enzymes involved in this process remain unexplored. In this study, we report that a tau class glutathione S-transferase (GST) from Carica papaya can degrade thiram. This enzyme was easily obtained by heterologous expression in Escherichia coli, showed low promiscuity toward other thiuram disulfides, and catalyzed thiram degradation under physiological reaction conditions. Site-directed mutagenesis indicated that G-site residue S67 shows a key influence for the enzymatic activity toward thiram, while mutation of residue S13, which reduced the GSH oxidase activity, did not significantly affect the thiram-degrading activity. The formation of dimethyl dithiocarbamate, which was subsequently converted into carbon disulfide, and dimethyl dithiocarbamoylsulfenic acid as the thiram degradation products suggested that thiram undergoes an alkaline hydrolysis that involves the rupture of the disulfide bond. Application of the GST selective inhibitor 4-chloro-7-nitro-2,1,3-benzoxadiazole reduced papaya peel thiram-degrading activity by 95%, indicating that this is the main degradation route of thiram in papaya. GST from Carica papaya also catalyzed the degradation of the fungicides chlorothalonil and thiabendazole, with residue S67 showing again a key influence for the enzymatic activity. These results fill an important knowledge gap in understanding the catalytic promiscuity of plant GSTs and reveal new insights into the fate and degradation products of thiram in fruits.

[Prognostic Significance of Progression of Disease within 24 Months in Mantle Cell Lymphoma].

OBJECTIVE: To investigate the effect of progression of disease within 24 months (POD24) on overall survival (OS) in patients with mantle cell lymphoma (MCL), and compare the clinical characteristics between POD24 and non-POD24 patients. METHODS: A retrospective analysis was performed on 50 MCL patients with treatment indications and regular treatment who were admitted to the Affiliated Hospital of Xuzhou Medical University from January 2010 to August 2020. According to the occurrence of POD24, the patients were grouped for prognostic evaluation and clinical characteristics comparison. RESULTS: Univariate Cox regression analysis showed that POD24, PLT, albumin, MIPI score, ECOG PS score, LDH were the factors influencing OS in newly diagnosed MCL patients (all P < 0.05). The results of multivariate Cox regression analysis showed that POD24ï¼»HR=16.797(95%CI : 3.671-76.861),P < 0.001ï¼½, albumin<40 g/Lï¼»HR=3.238(95%CI :1.095-9.572),P =0.034ï¼½ and ECOG PS score≥2ï¼»HR=4.005(95%CI :1.033-15.521),P =0.045ï¼½ were independent risk factors influencing OS in MCL patients. The incidence of PLT<100×109/L (33.3% vs 5.9%, P =0.033) and ECOG PS score ≥2 (45.5% vs 5.9%, P =0.040) were significantly higher in POD24 patients than those in non-POD24 patients. CONCLUSION: POD24 is an independent poor prognostic factor affecting the OS of MCL patients, and the patients with PLT<100×109/L and ECOG PS score≥2 at diagnosis have a higher probability of POD24.