Liver hydroxymethylbilane synthetase (EC 4.3.1.2) : an environmental and toxilogical kinetic study. The Effect of experimental design and circumstance on three common linearization methods used in determining the Michaelis-Menten kinetic constants

The kinetic constants Km and Vmax were determined for the deamination by adenosine deaminase of a series of analogues of adenosine containing "fraudulent" sugars. The configuration of the 2′-hydroxyl was found to be important for the binding of enzyme and substrate. The largest effect of changes in sugar structure was on the rate of breakdown of the enzyme–substrate complex to form products, i.e. Vmax. The nature of the configuration in the 3′-position was not important if the 2′-hydroxyl was trans to the glycosidic linkage; however, if the steric arrangement of the 2′-hydroxyl was cis to the glycosidic linkage, then Vmax showed a marked dependence on the nature of the 3′-substituent and its configuration. For instance, Vmax values were for arabinosyl adenine < 3′-deoxyarabinosyl adenine <lyxosyl adenine. 6-N-methyladenosine was found to be a competitive inhibitor of adenosine deaminase, with a Ki of 2 × 10−6M.

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“Best values” of Michaelis-Menten kinetic constants from experimental data

Analytical Biochemistry ◽

10.1016/0003-2697(68)90301-1 ◽

1968 ◽

Vol 22 (3) ◽

pp. 549-552 ◽

Cited By ~ 9

Author(s):

Stephen R. Cohen

Keyword(s):

Experimental Data ◽

Kinetic Constants ◽

Menten Kinetic

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Production of 5-Hydroxymethylfurfural from Direct Conversion of Cellulose Using Heteropolyacid/Nb2O5 as Catalyst

Catalysts ◽

10.3390/catal10121417 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1417

Author(s):

Jéssica Siqueira Mancilha Nogueira ◽

Vinícius Tomaz Santana ◽

Paulo Vitor Henrique ◽

Leandro Gonçalves de Aguiar ◽

João Paulo Alves Silva ◽

...

Keyword(s):

Experimental Data ◽

Experimental Design ◽

Kinetic Study ◽

Catalyst Concentration ◽

Direct Conversion ◽

Central Composite Rotatable Design ◽

Reaction Conditions ◽

Optimized Conditions ◽

Different Sources ◽

Central Composite

This study aimed to select the best reaction conditions to produce 5-hydroxymethylfurfural (HMF) from cellulose using heterogeneous catalyst based on a heteropolyacid (H3PW12O40—HPW) and Nb2O5. Initially, the influence of the temperature (160 or 200 °C), acetone:water ratio (50:50 or 75:25 v/v), cellulose load (5% or 10% w/v) and catalyst concentration (1% or 5% w/v) on HMF production from cellulose was evaluated through a Taguchi’s L16 screening experimental design. Afterwards, the main variables affecting this process, namely the temperature (160–240 °C) and acetone:water ratio (60:40–90:10 v/v), were optimized using a central composite rotatable design. Next, a kinetic study on HMF production from cellulose was carried out. Finally, HMF production from cellulose obtained from different biomass sources was evaluated. It was found that the reaction conditions able to result in maximum HMF yield, i.e., around 20%, were 200 °C, acetone:water ratio of 75:25 (v/v), 10% w/v of cellulose, and 5% w/v of catalyst concentration. The kinetic study revealed that the Langmuir–Hinshelwood–Hougen–Watson approach fit to the experimental data. Under the optimized conditions, the catalyst HPW/Nb2O5 was also effective in converting different sources of cellulose into HMF.

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