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741.
We have identified two types of invertases, one bound ionically and the other covalently to the particulate fraction in grains
of heat tolerant C 306 and heat susceptible WH 542 cultivars of wheat (Triticum aestivum L.). The cell walls contained a high level of invertase activity, of which 79.2–72.8% was extractable by 2 M NaCl and 14.9–21.1%
by 0.5% EDTA in C 306 and WH 542, respectively. The NaCl-released invertase constituted the predominant fraction. Using 5–100 mM
sucrose and pH range of 4.0–7.0, the apparent Michaelis constant (K
m, enzyme substrate affinity measure) of enzyme ranged from 5.73 to 16.06 mM for C 306 and from 6.08 to 19.86 mM for WH 542.
The V
max (maximum catalytic rate) values at these pH were higher in C 306 (0.63–11.04 μg sucrose hydrolysed min−1) than WH 542 (0.51–8.73 μg sucrose hydrolysed min−1). By employing photo-oxidation and by studying the effect of pH on K
m and V
max, the involvement of histidine and α-carboxyl groups at the active site of the enzyme was indicated. The two cultivars also
showed differential response in terms of thermodynamic properties of the enzyme i.e. energy of activation (E
a), enthalpy change (ΔH) and entropy change (ΔS). NaCl-released invertase showed differential response to metal ions in two cultivars suggesting their distinctive nature.
Mn2+, Cu2+, Hg2+, Mg2+, Zn2+ and Cd2+ were strong inhibitors in WH 542 as compared to C 306 while K+, Ca2+ were stimulators in both the cultivars. Overall the results suggest that genetic differences exist in wall bound invertase
properties of wheat grains as evident in its altered kinetic behaviour. 相似文献
742.
Enhanced production of glutaric acid by NADH oxidase and GabD-reinforced bioconversion from l-lysine
Yun-Gi Hong Yu-Mi Moon Tae-Rim Choi Hye-Rim Jung Soo-Yeon Yang Jung-Oh Ahn Jeong-Chan Joo Kyungmoon Park Yun-Gon Kim Shashi Kant Bhatia Yoo Kyung Lee Yung-Hun Yang 《Biotechnology and bioengineering》2019,116(2):333-341
Glutaric acid is a promising alternative chemical to phthalate plasticizer since it can be produced by the bioconversion of lysine. Though, recent studies have enabled the high-yield production of its precursor, 5-aminovaleric acid (AMV), glutaric acid production via the AMV pathway has been limited by the need for cofactors. Introduction of NAD(P)H oxidase (Nox) with GabTD enzyme remarkably diminished the demand for oxidized nicotinamide adenine dinucleotide (NAD+). Supply of oxygen through vigorous shaking had a significant effect on the conversion of AMV with a reduced requirement of NAD +. A high conversion rate was achieved in Nox coupled GabTD reaction under optimized expression vector, terrific broth (TB), and pH 8.5 at high cell density. Supplementary expression of GabD resulted in the production of 353 ± 35 mM glutaric acid with 88.3 ± 8.7% conversion from 400 mM AMV. Moreover, the reaction with a higher concentration of AMV could produce 528 ± 21 mM glutaric acid with 66.0 ± 2.7% conversion. In addition, the co-biotransformation strategy of GabTD and DavBA whole cells could produce 282 mM glutaric acid with 70.8% conversion from lysine, compared to the 111 mM glutaric acid yield from the combined GabTD–DavBA system. 相似文献
743.
Luca Orlando Borko Tanasijevic Mio Nakanishi Jennifer C. Reid Juan L. García-Rodríguez Kapil Dev Chauhan Deanna P. Porras Lili Aslostovar Justin D. Lu Zoya Shapovalova Ryan R. Mitchell Allison L. Boyd Mickie Bhatia 《Cell reports》2021,34(10):108818
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