BIOTECHNOLOGICAL STUDIES ON THE BIOSYNTHESIS OF DIMETHYLSULPHONIOPROPANOIC ACID IN DINOPHYCEAE AND CHILOROPHYCEAE

迈祖鲁湾海水中一年内生物源性二甲基硫化物（DMS）浓度在0.04 ~ 18.0马克DMS/l之间。虽然这些DMS浓度与叶绿素a浓度的发生率略有一致，但在双毛鞭毛虫（如micans原心藻和nagasakiense裸子藻）的赤潮水域中，DMS浓度与叶绿素a的浓度之间存在良好的相关性。夏季从沿海水域到大气的DMS平均通量的粗略估计约为10^3 mg S/m^<2。这是冬季通量的100倍。在“地震丸”和“白湖丸”航行期间，还测定了西、副热带太平洋表层海水和垂直水文剖面的DMS。在复光带DMS的垂直分布遵循初级生产的分布规律，在海面或近海面处最大，随着深度的增加而减小。在1%的光穿透水平下，DMS水平逐渐下降。日本外海和热带、亚热带太平洋表层水DMS平均浓度分别为611和265 ng DMS/l。由于DMS是海洋中主要的挥发性硫化合物，因此我们认为估算的DMS通过海空界面的转移对大气硫收支有重要贡献。叔砜化合物二甲基硫代丙酸（DMTP, =二甲基丙碱）是DMS的前体。蛋氨酸是甲酰鞭毛藻隐藻（Crypthecodinium cohnii）生物合成DMTP的有效前体。蛋氨酸的甲基、C-3和C-4碳以及硫原子被纳入DMTP，而蛋氨酸的C-1碳没有被纳入DMTP。结果表明，蛋氨酸通过脱羧、脱氨、氧化和甲基化转化为DMTP。从牛角菌中完全纯化了蛋氨酸脱羧酶，并对其进行了表征。该酶分子量约240 KDa，由2个亚基组成。Km值为16.3 mm。酶需要吡哆醛磷酸。该酶的n端氨基酸序列为ala - leu - x - trp - ser - asp - le- ser - arg -----。少

The concentration of biogenic dimethylsulphide(DMS) in the sea water in Maizuru Bay in one year ranged from 0.04 tO 18.0 mug DMS/l. Although these concentrations of DMS coincide slightly with the incidence of the concentration of chlorophyll a, a good correlation was obtained between concentration of DMS and chlorophyll a in red tide waters of dinoflagellates such as Prorocentrum micans and Gymnodinium nagasakiense. Rough estimates for the average flux of DMS from coastal water to the atmosphere during the summer are of the order of 10^3 mg S/m^<2.>d, a 100-fold increse over th winter flux. DMS in surface seawater and vertical hydrographic profiles were also determined in the western, subtropical Pacific Ocean during the cruises of the Seisui-maru and Hakuho-maru. The vertical distribution of DMS in the euphotic zone follows that of primary production, with a maximum at or near the ocean surfce and a decrease with depth. Below the level of 1% light penetration, DMS levels decline gradu … More ally. The mean DMS concentrations in the surface water of the sea off Japan and the tropical and subtropical Pacific Ocean were 611 and 265 ng DMS/l, respectively. Since DMS is the major volatile sulphur compound in the ocean, it is suggested that estimated DMS transfer across the sea-air interface contributes significantly to the atmospheric sulphur budget.The tertiary sulphonium compound dimethylthiopropanoic acid(DMTP, = dimethylpropiothetine) is a precursor of DMS.Methionine is an efficient precursor for the biosynthesis of DMTP in the dinoflagellate Crypthecodinium cohnii. The methyl group, C-3 and C-4 carbons, and sulphur atoms of methionine were incorporated into DMTP, whereas C-1 carbon of methionine was not incorporated into DMTP.The results indicate that methionine is converted to DMTP by decarboxylation, deamination, oxidation, and methylation.Methionine decarboxylase was completely purified from C.cohnii and characterized. The molecular weight of this enzyme is about 240 KDa, consit of 2 subunits. Km value is 16.3 mM.The enzyme requires pyridoxalphosphate. The N-terminal amino acid sequence of the enzyme is Ala-Leu-X-Trp-Ser-Asp-lle-Ser-Arg-----. Less