pH-Dependent metabolism of thiosulfate and sulfur globules in the chemolithotrophic marine bacterium Thiomicrospira crunogena

Respiring cells of the chemolithotrophic bacterium Thiomicrospira crunogena produced sulfur globules from the sulfane sulfur of thiosulfate below pH 7, and consumed the globules above pH 7. The switch in metabolism was immediate and reversible upon titration of the culture. The consumed sulfur globules remained in a membrane-bound form and were not oxidized unless the medium was depleted of thiosulfate. Sulfur globule production but not uptake was blocked by azide. Anoxia, thiol-binding agents, and inhibitors of protein synthesis blocked globule uptake. Transitory accumulations of sulfite and polythionates appeared to be reaction products of thiosulfate and sulfur globules. A model depicting the pH sensitivity and biochemistry of sulfur globule production and consumption is proposed.     

碳酸酐酶在红细胞分化发育过程中的功能研究

目前红系分化调控相关的研究主要集中在细胞因子、转录因子、lncRNA及表观遗传方面,为了对红系分化调控机制进行更加深入的解析,研究了碳酸酐酶在红系分化中的功能。碳酸酐酶可以高效催化二氧化碳的水合,但它在红细胞发育过程中的功能尚不清楚。利用脐带血来源的CD34⁺细胞在体外进行红细胞诱导分化,在分化过程中通过慢病毒介导的基因敲降的方法能够降低碳酸酐酶1和碳酸酐酶2的表达,并使用流式细胞仪检测红细胞的生成和分化效率。研究结果表明,与对照组相比,碳酸酐酶1的表达缺陷使红细胞的晚期分化明显受阻,而碳酸酐酶2的表达缺陷则将红细胞的分化阻滞在早期阶段。研究结果表明,虽然作用窗口不同,但碳酸酐酶1和碳酸酐酶2在红系分化的过程中均发挥着重要的调控作用,这一发现对将来在体外红细胞生成具有指导意义。     

Carbonic Anhydrase and the Regulation of Photosynthesis

THE role of CO₂ in the regulation of photosynthetic and respiratory metabolism in plants is little understood in the unicellular alga Chlorella pyrenoidosa; for example, after autotrophic growth in high CO₂ (5·5% by volume), transfer to a CO₂ concentration about ten times less than the concentration in air results initially in low rates of photosynthesis characterized by the virtual absence of the Calvin cycle¹ of CO₂ fixation². An induction period of about 2 h is necessary before normal photosynthetic rates are established. Cells grown in air (0.03% CO₂) do not show this effect and photosynthesize at comparatively high rates even in very low concentrations of CO₂.     

Up-Regulation of Carbonic Anhydrase Isozyme IV in CNS Myelin of Mice Genetically Deficient in Carbonic Anhydrase II

Abstract: Carbonic anhydrase (CA) II is the major CA isozyme in the brain, where it participates in acid-base homeostasis, fluid transport, and myelin synthesis. The CA II deficiency [CA(II)D] mutation in the mouse results in structural changes in the glial cells in the CNS and in decreased susceptibility to seizures, but no detectable changes in myelin yield and ultrastructure. We compared the CA isozymes in brain and spinal cord fractions, as well as in purified myelin, between CA(II)D and control mice. CA(II)D resulted in a much lower total CA specific activity in all tissues examined but in higher CA IV specific activities in soluble and membrane-associated fractions and pure myelin. Western blots of purified myelin showed a band corresponding to CA IV in CA(II)D mice. This band was weak or undetectable in myelin samples from normal mice. Immunocytochemical staining demonstrated CA IV in oligodendrocytes and myelinated tracts in normal mouse brains and stronger staining of the same structures in brains of CA(II)D mutants. We conclude that CA(II)D mutation in the mouse up-regulates CNS CA IV. We speculate that this up-regulation could mitigate the effect of CA(II)D on myelin formation and maintenance.     

碳酸酐酶Ⅳ与人类疾病

碳酸酐酶4（carbonic anhydrase 4,CAIV）是12种人类相关碳酸酐酶中的一员,主要通过糖基磷脂酰基醇锚定在细胞质膜上。哺乳动物的多个器官有CAIV的表达。CAIV高效催化CO2的水化和HCO3–的脱水反应,在尿液酸化、肺泡换气等生理反应中起重要作用。CAIV基因表达的变化、结构稳定性的破坏和活性的改变等均与人类多种疾病的发生发展密切相关。CAIV还可以作为药物治疗靶点应用于疾病治疗。为此,该文就CAIV与人类相关疾病发生的病理生理机制作一综述。     

Carbonic Anhydrase Polymorphism in Cattle and Swine

Two electrophoretically different carbonic anhydrase (Ca) isoenzymes have been demonstrated in cattle where their presence is presumed to be controlled by codominant allelic genes (Sartore & Bernoco 1966). Previous reports of Ca polymorphism in swine are not available.     

The Genome of Deep-Sea Vent Chemolithoautotroph Thiomicrospira crunogena XCL-2

Presented here is the complete genome sequence of Thiomicrospira crunogena XCL-2, representative of ubiquitous chemolithoautotrophic sulfur-oxidizing bacteria isolated from deep-sea hydrothermal vents. This gammaproteobacterium has a single chromosome (2,427,734 base pairs), and its genome illustrates many of the adaptations that have enabled it to thrive at vents globally. It has 14 methyl-accepting chemotaxis protein genes, including four that may assist in positioning it in the redoxcline. A relative abundance of coding sequences (CDSs) encoding regulatory proteins likely control the expression of genes encoding carboxysomes, multiple dissolved inorganic nitrogen and phosphate transporters, as well as a phosphonate operon, which provide this species with a variety of options for acquiring these substrates from the environment. Thiom. crunogena XCL-2 is unusual among obligate sulfur-oxidizing bacteria in relying on the Sox system for the oxidation of reduced sulfur compounds. The genome has characteristics consistent with an obligately chemolithoautotrophic lifestyle, including few transporters predicted to have organic allocrits, and Calvin-Benson-Bassham cycle CDSs scattered throughout the genome.     

Loss of the Transit Peptide and an Increase in Gene Expression of an Ancestral Chloroplastic Carbonic Anhydrase Were Instrumental in the Evolution of the Cytosolic C4 Carbonic Anhydrase in Flaveria

C₄ photosynthesis has evolved multiple times from ancestral C₃ species. Carbonic anhydrase (CA) catalyzes the reversible hydration of CO₂ and is involved in both C₃ and C₄ photosynthesis; however, its roles and the intercellular and intracellular locations of the majority of its activity differ between C₃ and C₄ plants. To understand the molecular changes underlying the evolution of the C₄ pathway, three cDNAs encoding distinct β-CAs (CA1, CA2, and CA3) were isolated from the leaves of the C₃ plant Flaveria pringlei. The phylogenetic relationship of the F. pringlei proteins with other embryophyte β-CAs was reconstructed. Gene expression and protein localization patterns showed that CA1 and CA3 demonstrate high expression in leaves and their products localize to the chloroplast, while CA2 expression is low in all organs examined and encodes a cytosolic enzyme. The roles of the F. pringlei enzymes were considered in light of these results, other angiosperm β-CAs, and Arabidopsis (Arabidopsis thaliana) “omics” data. All three F. pringlei CAs have orthologs in the closely related C₄ plant Flaveria bidentis, and comparisons of ortholog sequences, expression patterns, and intracellular locations of their products indicated that CA1 and CA2 have maintained their ancestral role in C₄ plants, whereas modifications to the C₃ CA3 gene led to the evolution of the CA isoform that catalyzes the first step in the C₄ photosynthetic pathway. These changes included the loss of the chloroplast transit peptide and an increase in gene expression, which resulted in the high levels of CA activity seen in the cytosol of C₄ mesophyll cells.     

Expression and Functional Study of Single Mutations of Carbonic Anhydrase 8 in Neuronal Cells

Cellular and Molecular Neurobiology - Carbonic anhydrase 8 (CA8), an isozyme of α-carbonic anhydrases, lacks the ability to catalyze the reversible hydration of CO2 to bicarbonate and proton....     

Carbonic Anhydrase in the Marine Alga Ulva pertusa

The preparation of stable samples containing carbonic anhydrase from Ulva pertusa was achieved by using artificial sea water and 10 mM cysteine solution adjusted to pH 8.2 instead of 10 mM cysteine solution alone. When the sample was stored at 0°C in darkness the enzyme activity was retained for about 24 h. In contrast to the results obtained with land plants in previous works a remarkable inhibitory effect of low concentrations of sulfanilamide and Diamox (2-acetylamino-1,3,4-thiadiazole-5-sulfonamide) on the activity of the enzyme was observed.     

Carbonic Anhydrase of Chlamydomonas: Purification and Studies on its Induction Using Antiserum against Chlamydomonas Carbonic Anhydrase

Carbonic anhydrase (EC 4.2.1.1 [EC] ; CA) was purified by affinitychromatography from cells of the unicellular green alga Chlamydomonasreinhardtii which had been grown photoautotrophically in ordinaryair. Antiserum raised in rabbit against this purified CA crossreactedwith Chlamydomonas CA but not with spinach leaf CA nor bovineerythrocyte CA. When the CO₂ concentration provided to the algalcells was decreased from 4% to the ordinary air level (0.04%),CA activity and the content of CA protein determined by theimmunodiffusion test showed parallel increases. In contrast,when the CO₂ concentration was raised from air level to 4% CO₂CA activity and its content expressed on the basis of culturevolume remained rather constant. These results indicate thatsynthesis of the CA protein is induced when the CO₂ concentrationis lowered from 4 to 0.04% during algal growth. On the otherhand, the synthesis of CA stops when CO₂ concentration is raisedfrom air level to 4%. (Received June 30, 1984; Accepted October 8, 1984)