DXP Reductoisomerase: Reaction of the Substrate in Pieces Reveals a Catalytic Role for the Nonreacting Phosphodianion Group

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

Download Full-text

Evidence for a catalytic role of glutamic acid 129 in the NAD-glycohydrolase activity of the pertussis toxin S1 subunit.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(20)80504-3 ◽

1993 ◽

Vol 268 (32) ◽

pp. 24149-24155

Author(s):

R Antoine ◽

A Tallett ◽

S van Heyningen ◽

C Locht

Keyword(s):

Glutamic Acid ◽

Pertussis Toxin ◽

Nad Glycohydrolase ◽

Catalytic Role

Download Full-text

The Aspergillus nidulans xprF Gene Encodes a Hexokinase-like Protein Involved in the Regulation of Extracellular Proteases

Genetics ◽

10.1093/genetics/156.4.1559 ◽

2000 ◽

Vol 156 (4) ◽

pp. 1559-1571 ◽

Cited By ~ 1

Author(s):

Margaret E Katz ◽

Amir Masoumi ◽

Stephen R Burrows ◽

Carolyn G Shirtliff ◽

Brian F Cheetham

Keyword(s):

Sequence Analysis ◽

Aspergillus Nidulans ◽

Carbon Limitation ◽

Extracellular Proteases ◽

Nonsense Mutations ◽

Acid Protein ◽

Catalytic Role ◽

New Type ◽

Protease Deficient ◽

A Minor

Abstract The extracellular proteases of Aspergillus nidulans are produced in response to limitation of carbon, nitrogen, or sulfur, even in the absence of exogenous protein. Mutations in the A. nidulans xprF and xprG genes have been shown to result in elevated levels of extracellular protease in response to carbon limitation. The xprF gene was isolated and sequence analysis indicates that it encodes a 615-amino-acid protein, which represents a new type of fungal hexokinase or hexokinase-like protein. In addition to their catalytic role, hexokinases are thought to be involved in triggering carbon catabolite repression. Sequence analysis of the xprF1 and xprF2 alleles showed that both alleles contain nonsense mutations. No loss of glucose or fructose phosphorylating activity was detected in xprF1 or xprF2 mutants. There are two possible explanations for this observation: (1) the xprF gene may encode a minor hexokinase or (2) the xprF gene may encode a protein with no hexose phosphorylating activity. Genetic evidence suggests that the xprF and xprG genes are involved in the same regulatory pathway. Support for this hypothesis was provided by the identification of a new class of xprG- mutation that suppresses the xprF1 mutation and results in a protease-deficient phenotype.

Download Full-text

Catalytic role of assembled Ce Lewis acid sites over ceria for electrocatalytic conversion of dinitrogen to ammonia

Journal of Energy Chemistry ◽

10.1016/j.jechem.2021.01.016 ◽

2021 ◽

Vol 60 ◽

pp. 249-258

Author(s):

Jiamin Qi ◽

Shulan Zhou ◽

Ke Xie ◽

Sen Lin

Keyword(s):

Lewis Acid ◽

Acid Sites ◽

Lewis Acid Sites ◽

Catalytic Role

Download Full-text

Flammable gases produced by TiO2 nanoparticles under magnetic stirring in water

Friction ◽

10.1007/s40544-021-0505-5 ◽

2021 ◽

Author(s):

Pengcheng Li ◽

Chongyang Tang ◽

Xiangheng Xiao ◽

Yanmin Jia ◽

Wanping Chen

Keyword(s):

Tio2 Nanoparticles ◽

Quartz Glass ◽

Dye Degradation ◽

Mechanical Energy ◽

Chemical Energy ◽

Magnetic Stirring ◽

Catalytic Role ◽

Nanostructured Semiconductors

AbstractThe friction between nanomaterials and Teflon magnetic stirring rods has recently drawn much attention for its role in dye degradation by magnetic stirring in dark. Presently the friction between TiO2 nanoparticles and magnetic stirring rods in water has been deliberately enhanced and explored. As much as 1.00 g TiO2 nanoparticles were dispersed in 50 mL water in 100 mL quartz glass reactor, which got gas-closed with about 50 mL air and a Teflon magnetic stirring rod in it. The suspension in the reactor was magnetically stirred in dark. Flammable gases of 22.00 ppm CO, 2.45 ppm CH4, and 0.75 ppm H2 were surprisingly observed after 50 h of magnetic stirring. For reference, only 1.78 ppm CO, 2.17 ppm CH4, and 0.33 ppm H2 were obtained after the same time of magnetic stirring without TiO2 nanoparticles. Four magnetic stirring rods were simultaneously employed to further enhance the stirring, and as much as 30.04 ppm CO, 2.61 ppm CH4, and 8.98 ppm H2 were produced after 50 h of magnetic stirring. A mechanism for the catalytic role of TiO2 nanoparticles in producing the flammable gases is established, in which mechanical energy is absorbed through friction by TiO2 nanoparticles and converted into chemical energy for the reduction of CO2 and H2O. This finding clearly demonstrates a great potential for nanostructured semiconductors to utilize mechanical energy through friction for the production of flammable gases.

Download Full-text