1.Synthesis of chiral 2-alkanols from n-alkanes by a P. putida whole-cell biocatalyst.
Tieves F1, Erenburg IN1, Mahmoud O1, Urlacher VB1. Biotechnol Bioeng. 2016 Feb 16. doi: 10.1002/bit.25953. [Epub ahead of print]
The cytochrome P450 monooxygenase CYP154A8 from Nocardia farcinica was previously found to catalyze hydroxylation of linear alkanes (C7 -C9 ) with a high regio- and stereoselectivity. The objective of this study was to integrate CYP154A8 along with suitable redox partners into a whole-cell system for the production of chiral 2-alkanols starting from alkanes. Both recombinant Escherichia coli and Pseudomonas putida whole-cell biocatalysts tested for this purpose showed the ability to produce chiral alkanols, but a solvent tolerant P. putida strain demonstrated several advantages in the applied biphasic reaction system. The optimized P. putida whole-cell systems produced ∼16 mM (S)-2-octanol with 87% ee from octane, which is more than 7-fold higher than the previously described system with isolated enzymes. The achieved enantiopurity of the product could further be increased up to 99% ee by adding an alcohol dehydrogenase (ADH) to the alkane-oxidizing P.
2.Atrial Anti-Arrhythmic Effects of Heptanol in Langendorff-Perfused Mouse Hearts.
Tse G1, Tse V2, Yeo JM3, Sun B4. PLoS One. 2016 Feb 12;11(2):e0148858. doi: 10.1371/journal.pone.0148858. eCollection 2016.
Acute effects of heptanol (0.1 to 2 mM) on atrial electrophysiology were explored in Langendorff-perfused mouse hearts. Left atrial bipolar electrogram or monophasic action potential recordings were obtained during right atrial stimulation. Regular pacing at 8 Hz elicited atrial activity in 11 out of 11 hearts without inducing atrial arrhythmias. Programmed electrical stimulation using a S1S2 protocol provoked atrial tachy-arrhythmias in 9 of 17 hearts. In the initially arrhythmic group, 2 mM heptanol exerted anti-arrhythmic effects (Fisher's exact test, P < 0.05) and increased atrial effective refractory period (ERP) from 26.0 ± 1.9 to 57.1 ± 2.5 ms (ANOVA, P < 0.001) despite increasing activation latency from 18.7 ± 1.1 to 28.9 ± 2.1 ms (P < 0.001) and leaving action potential duration at 90% repolarization (APD90) unaltered (25.6 ± 1.2 vs. 27.2 ± 1.2 ms; P > 0.05), which led to increases in ERP/latency ratio from 1.4 ± 0.1 to 2.
3.Ventricular anti-arrhythmic effects of heptanol in hypokalaemic, Langendorff-perfused mouse hearts.
Tse G1, Tse V2, Yeo JM3. Biomed Rep. 2016 Mar;4(3):313-324. Epub 2016 Jan 21.
Ventricular arrhythmic and electrophysiological properties were examined during normokalaemia (5.2 mM [K+]), hypokalaemia (3 mM [K+]) or hypokalaemia in the presence of 0.1 or 2 mM heptanol in Langendorff-perfused mouse hearts. Left ventricular epicardial or endocardial monophasic action potential recordings were obtained during right ventricular pacing. Hypokalaemia induced ventricular premature beats (VPBs) in 5 of 7 and ventricular tachycardia (VT) in 6 of 7 hearts (P<0.01), prolonged action potential durations (APD90) from 36.2±1.7 to 55.7±2.0 msec (P<0.01) and shortened ventricular effective refractory periods (VERPs) from 44.5±4.0 to 28.9±3.8 msec (P<0.01) without altering conduction velocities (CVs) (0.17±0.01 m/sec, P>0.05), reducing excitation wavelengths (λ, CV × VERP) from 7.9±1.1 to 5.1±0.3 mm (P<0.05) while increasing critical intervals (CI, APD90-VERP) from -8.3±4.3 to 26.9±2.0 msec (P>0.001). Heptanol (0.