Structural and Biochemical Analyses of the Butanol Dehydrogenase from Fusobacterium nucleatum.

Butanol dehydrogenase (BDH) plays a significant role in the biosynthesis of butanol in bacteria by catalyzing butanal conversion to butanol at the expense of the NAD(P)H cofactor. BDH is an attractive enzyme for industrial application in butanol production; however, its molecular function remains largely uncharacterized. In this study, we found that Fusobacterium nucleatum YqdH (FnYqdH) converts aldehyde into alcohol by utilizing NAD(P)H, with broad substrate specificity toward aldehydes but not alcohols. An in vitro metal ion substitution experiment showed that FnYqdH has higher enzyme activity in the presence of Co2+. Crystal structures of FnYqdH, in its apo and complexed forms (with NAD and Co2+), were determined at 1.98 and 2.72 Å resolution, respectively. The crystal structure of apo- and cofactor-binding states of FnYqdH showed an open conformation between the nucleotide binding and catalytic domain. Key residues involved in the catalytic and cofactor-binding sites of FnYqdH were identified by mutagenesis and microscale thermophoresis assays. The structural conformation and preferred optimal metal ion of FnYqdH differed from that of TmBDH (homolog protein of FnYqdH). Overall, we proposed an alternative model for putative proton relay in FnYqdH, thereby providing better insight into the molecular function of BDH.

[Most effective daily dose and use method of mannitol in patients with cerebral hemorrhage at acute stage].

OBJECTIVE: To explore the most effective daily dose and use method of mannitol in reducing intracranial pressure in patients with cerebral hemorrhage in acute stage. METHODS: One hundred and eighteen cerebral hemorrhage patients with elevated intracranial pressure, 74 males and 44 females, aged (58 +/- 11) (33-80), that had undergone cranial CT scanning to calculate the volume of hemorrhage, were divided into 4 groups treated with 20% mannitol 125 ml: 32 cases treated q 4 h, 35 cases treated q 6 h, 25 cases treated q 8 h, and 26 cases treated q 12 h. The everyday doses of mannitol were recorded. Intracranial pressure was monitored daily by NIP-200 noninvasive intracranial pressure apparatus. The difference between the very day and that of the last day (effect of decreasing intracranial pressure per day) was calculated. Multivariate regression analysis was conducted. RESULTS: The average saturation dosage of mannitol was 750-6000 (3504 +/- 1085) ml, the time from the hospitalization till the saturation dosage was 1-8 (4.5 +/- 1.5) d. The average intracranial pressure at admission was 330-698 (486 +/- 93) mm H2O, the average intracranial pressure when mannitol reached the saturation dosage was 160-378 (253 +/- 52) mm H2O. The effect of reduction of intracranial pressure was not associated with age (P > 0.05). The effects of reducing intracranial pressure in the 1st, 2nd, 3rd, and 4th day were associated with the volume of hematoma and mannitol doses (all P < 0.01). Best effects of reducing the intracranial pressure in the 1st, 2nd, 3rd, and 4th day could be reached when 20% mannitol 125 ml was used every 4 hours. CONCLUSIONS: Mannitol use every 4 hours per day has evident effect of reducing the intracranial pressure in the 1st, 2nd, 3rd, and 4th day, then mannitol should be used temporarily according to the intracranial pressure after the 5th day. Mannitol should not be used for more than 8 days.