1.Efficient bioconversion of L-glutamate to γ-aminobutyric acid by Lactobacillus brevis resting cells.
Shi X1, Chang C1, Ma S1, Cheng Y1, Zhang J1, Gao Q2. J Ind Microbiol Biotechnol. 2016 May 7. [Epub ahead of print]
This work investigated the efficient bioconversion process of L-glutamate to GABA by Lactobacillus brevis TCCC 13007 resting cells. The optimal bioconversion system was composed of 50 g/L 48 h cultivated wet resting cells, 0.1 mM pyridoxal phosphate in glutamate-containing 0.6 M citrate buffer (pH 4.5) and performed at 45 °C and 180 rpm. By 10 h bioconversion at the ratio of 80 g/L L-glutamic acid to 240 g/L monosodium glutamate, the final titer of GABA reached 201.18 g/L at the molar bioconversion ratio of 99.4 %. This process presents a potential for industrial and commercial applications and also offers a promising feasibility of continuous GABA production coupled with fermentation. Besides, the built kinetics model revealed that the optimum operating conditions were 45 °C and pH 4.5, and the bioconversion kinetics at low ranges of substrate concentration (0 < S < 80 g/L) was assumed to follow the classical Michaelis-Menten equation.
2.Synthesis of barbituric acid containing nucleotides and their implications for the origin of primitive informational polymers.
Mungi CV1, Singh SK2, Chugh J3, Rajamani S1. Phys Chem Chem Phys. 2016 May 6. [Epub ahead of print]
Given that all processes in modern biology are encoded and orchestrated by polymers, the origin of informational molecules had to be a crucial and significant step in the origin of life on Earth. An important molecule in this context is RNA that is thought to have allowed the transition from chemistry to biology. However, the RNA molecule is comprised of intramolecular bonds which are prone to hydrolysis, especially so under the harsh conditions of the early Earth. Furthermore, the formation of nucleotides with extant bases and their subsequent polymerization have both been problematic, to say the least. Alternate heterocycles, in contrast, have resulted in nucleosides in higher yields, suggesting a viable and prebiotically relevant solution to the longstanding "nucleoside problem". In the present study, we have synthesized a nucleotide using ribose 5'-monophosphate (rMP) and barbituric acid (BA), as the base analog, using dry-heating conditions that are thought to be prevalent in several regimes of the early Earth.
3.The role of red blood cell S-nitrosation in nitrite bioactivation and its modulation by leucine and glucose.
Wajih N1, Liu X1, Shetty P1, Basu S2, Wu H3, Hogg N4, Patel RP5, Furdui CM3, Kim-Shapiro DB6. Redox Biol. 2016 Apr 30;8:415-421. doi: 10.1016/j.redox.2016.04.004. [Epub ahead of print]
Previous work has shown that red blood cells (RBCs) reduce nitrite to NO under conditions of low oxygen. Strong support for the ability of red blood cells to promote nitrite bioactivation comes from using platelet activation as a NO-sensitive process. Whereas addition of nitrite to platelet rich plasma in the absence of RBCs has no effect on inhibition of platelet activation, when RBCs are present platelet activation is inhibited by an NO-dependent mechanism that is potentiated under hypoxia. In this paper, we demonstrate that nitrite bioactivation by RBCs is blunted by physiologically-relevant concentrations of nutrients including glucose and the important signaling amino acid leucine. Our mechanistic investigations demonstrate that RBC mediated nitrite bioactivation is largely dependent on nitrosation of RBC surface proteins. These data suggest a new expanded paradigm where RBC mediated nitrite bioactivation not only directs blood flow to areas of low oxygen but also to areas of low nutrients.
