Structural and mechanistic investigations on CC bond forming α-oxoamine synthase allowing L-glutamate as substrate.

Carbon­carbon (C-C) bonds serve as the fundamental structural backbone of organic molecules. As a critical CC bond forming enzyme, α-oxoamine synthase is responsible for the synthesis of α-amino ketones by performing the condensation reaction between amino acids and acyl-CoAs. We previously identified an α-oxoamine synthase (AOS), named as Alb29, involved in albogrisin biosynthesis in Streptomyces albogriseolus MGR072. This enzyme belongs to the α-oxoamine synthase family, a subfamily under the pyridoxal 5'-phosphate (PLP) dependent enzyme superfamily. In this study, we report the crystal structures of Alb29 bound to PLP and L-Glu, which provide the atomic-level structural insights into the substrate recognition by Alb29. We discover that Alb29 can catalyze the amino transformation from L-Gln to L-Glu, besides the condensation of L-Glu with ß-methylcrotonyl coenzyme A. Subsequent structural analysis has revealed that one flexible loop in Alb29 plays an important role in both amino transformation and condensation. Based on the crystal structure of the S87G mutant in the loop region, we capture two distinct conformations of the flexible loop in the active site, compared with the wild-type Alb29. Our study offers valuable insights into the catalytic mechanism underlying substrate recognition of Alb29.

[Experimental study of electroacupuncture improving the obstruction of vestibular microcirculation in vertebrobasilar insufficiency and the effect on vestibulo-ocular reflex].

AIM: To investigate the mechanism of EA improving the obstruction of inner ear microcirculation and the effect on the vestibulo-ocular reflex (VOR) by comparing the effects of electroacupuncture (EA) with sibelium (flunarizine hydrochloride) on vertebrobasilar insufficiency(VBI). METHODS: Injected with sclerosant-775 injection into the solt tissue on the left side of cervical vertebral transverse processes of rabbits to set up the vertebral artery type of cervical spondylosis (VCS) models. Electronystagmography (ENG) induced by linear acceleration (LA) and horizontal rotation (HR), the transcranial Doppler (TCD), laser Doppler flowmetry (LDF) and hemorheology were used to measure changes of the frequencies of nystagmus, the hemodynamics in the basilar artery (BA), inner ear blood flow(IEBF) and blood viscosity in VBI rabbits. RESULTS: The frequencies of ENG, the velocity of blood flow in BA and IEBF decreased obviously, and whole blood middle where viscosity, whole blood lower where viscosity and erythrocyte distortion index ( EDI) increased significantly in the model group. Sibelium could reduce whole blood viscosity and EDI, and increased the systolic phase velocity (Vs) of blood flow in BA, but had no effect on diastolic phase velocity (Vd) and mean velocity (Vm). EA could not reduce the viscosity of blood and EDI, but had more significant effects on improving IEBF and ENG induced by LA than those of sibelium,and had the tendency of increasing Vs, Vd and Vm. EA and sibelium had no effect on improving ENG induced by HR. CONCLUSION: Inner ear microcirculation obstruction caused by VBI can induce dysfunctions of vestibule cyst macula and horizontal semicircular canals. EA may depend upon the neurohumoral regulation to improve VBI, and ameliorate inner ear blood supply obstruction by enhancing mechanism of local adjusting for microcirculation in the inner ear to recover vestibular cyst macula irritability for LA chiefly. There exist complicated mechanism that EA adjusts blood flow distribution and vestibular signal transduction in vestibular organ in VBI model likely, and remain to be researched deeply.

[Effects of acupuncture at different periods on circadian rhythms of locomotor activity and core body temperature in hamsters].

OBJECTIVE: To explore the time law of electroacupuncture in regulation of circadian rhythms of the organism. METHODS: Effects of electroacupuncture at "Shenshu" (BL 23) at Zi, Wu, Mao and You periods on circadian rhythms of locomotor activity and core body temperature in hamsters were observed with chronobiological research methods. RESULTS: Electroacupuncture at Wu period could decrease the amplitude of locomotor activity rhythm (P < 0.05), at Mao period could delay the peak phase of circadian rhythm and at You period could advance the peak phase of circadian rhythm (both P < 0.05); and electroacupuncture at Mao period could delay 22.36 degrees and at You period advance 39.32 degrees for the rhythm peak of the circadian rhythm of core body temperature. CONCLUSION: Acupuncture has a certain effect on circadian rhythm of locomotor activity and core body temperature.