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

麦祖鲁湾海水中生物二甲基硫化物(DMS)浓度一年的变化范围为0.04~18.0mug DMS/L，虽然DMS浓度与藻类赤潮水体中叶绿素a的浓度变化规律略有吻合，但与长崎原甲藻和长崎裸甲藻等赤潮水体中的叶绿素a浓度有较好的相关性。粗略估计夏季近岸海域DMS向大气的平均通量约为10^3 mg S/m~(-2)，比冬季增加100倍。在震水丸号和白豪丸号巡航期间，还测定了西太平洋、副热带太平洋表层海水和垂直水文剖面中的DMS。DMS在真光层的垂直分布遵循初级生产力的垂直分布，最大值出现在海面或其附近，并随深度的增加而减小。低于1%光透过率的水平，二甲基硫水平下降等级…更像是盟友。日本近海和热带、亚热带太平洋表层水中DMS的平均浓度分别为611ngDMS/L和265ngDMS/L。由于DMS是海洋中主要的挥发性硫化合物，推测DMS通过海-气界面的转移对大气硫收支有重要贡献。三价硫化合物二甲硫丙酸(DMTP，=二甲基丙硫氨酸)是DMS的前体。蛋氨酸是隐甲藻DMTP生物合成的有效前体。甲硫氨酸的甲基、C-3、C-4碳和硫原子被引入到DMTP中，而蛋氨酸的C-1碳没有进入DMTP。结果表明，蛋氨酸通过脱羧基、脱氨基、氧化和甲基化转化为DMTP。该酶的相对分子质量为240 KDa，由2个亚基组成。Km值为16.3mM。该酶需要吡哆醛磷酸。该酶N端氨基酸序列为Ala-Leu-X-Trp-Ser-Asp-Lle-Ser-Arg-。较少

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