beta-Glucosidase from Flavobacterium meningosepticum (Fbgl) catalyses the hydrolysis of beta-1,4-glucosidic bonds via a two-step double-displacement mechanism in which two amino acid residues act as nucleophile and acid/base catalyst. Definitive identification of these two residues is provided by the two active-site-directed inactivators, 2',4'-dinitrophenyl-2-deoxy-2-fluoro-beta-d-glucoside (2FDNPG) and N-bromoacetyl-beta-d-glucosylamine (NBGN), which stoichiometrically label the nucleophile and the acid/base catalyst of Fbgl, respectively. Pseudo-first-order inactivation rate constants (k(i)) of 0.25+/-0.01 and 0.05+/-0.01 min(-1) and dissociation constants (K(i)) of 90+/-15 and 4.4+/-0.2 mM are determined for 2FDNPG and NBGN, respectively. Proteolytic digestion of the labelled proteins, followed by peptide mapping and tandem MS analysis identify Asp-247 and Glu-473 as the catalytic nucleophile and acid/base residues, respectively, of Fbgl. This study confirms that the catalytic nucleophile of family 3 glycohydrolase is conserved across sub-families. However, different sub-families may have unique general acid/base catalysts.

A simple Schiff-base receptor 2 was prepared. It exhibits an “off-on-type” mode with high sensitivity in the presence of Al3+. The receptor 2 exhibited a high association constant with submicromolar detection for Al3+ in EtOH–H2O (95:5 v/v) solution. The addition of EDTA quenches the fluorescence of the receptor 2·Al3+ complex offering receptor 2 as a reversible chemosensor.

Acute myeloid leukemia (AML), a very rare type of cancer, generally affects patients over 50 years old. While clinical drugs to treat advanced stages of AML exist, the disease becomes increasingly resistant to therapies. Euphorbia formosana Hayata (EF) is a native Taiwanese medicinal plant used to treat rheumatism, liver cirrhosis, herpes zoster, scabies, and photoaging, along with tumor suppression. However, the mechanisms by OPEN ACCESSMolecules 2013, 18 1950 which it suppresses tumors have not been explored. Here, we provide molecular evidence that a hot-water extract of Euphorbia formosana (EFW) selectively inhibited the growth of human leukemic cancer cells more than other solid human cancer cell lines. Most importantly, the plant extract had limited toxicity toward healthy peripheral blood mononuclear cells (PBMCs). After THP-1 leukemic cells were treated with 50-100 µg/mL EFW for one day, the S phase DNA content of the cells increased, while treatment with 200-400 µg/mL caused the cells to accumulate in the G0/G1 phase. Notably, EFW did not affect A-549 lung cancer cells. The effectiveness of EFW against THP-1 cells may be through caspase-dependent apoptosis in leukemic cells, which is mediated through the Fas and mitochondrial pathways. The potent antileukemic activity of EFW in vitro warrants further investigation of this plant to treat leukemias and other malignancies.

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