Diatom assemblages in the surface water of the Indian Sector of the Antarctic Surface Water in summer of 1999/2000

Abundance and species composition of diatom assemblages in surface water of the Indian Sector of the Antarctic Surface Water of the Southern Ocean were examined using samples gathered during the JARE-41 Cruise of the icebreaker Shirase in the summer of 1999/2000. On the westward leg (Leg 1), abundance of the diatom assemblage was geographically rather uniform, while species composition was different geographically in mosaic manner. Dominant species on Leg 1 were the pennate Pseudo-nitzschia spp. and the centric Dactyliosolen tenuijunctus, Chaetoceros sp. cf. dichaeta and Chaetoceros neglectus. On the eastward leg (Leg 2), abundance and species composition were different east and west of 60°E. The community to the west was large in abundance and dominated by D. tenuijunctus, while that to the east was small and dominated by the pennate Fragilariopsis species. These diatom assemblages were grouped into four clusters on Leg 1 and three on Leg 2. Mosaic distribution of the clusters was again evident on Leg 1, while rather simple east-west difference was the case on Leg 2. These geographical variations seem to be affected by local sea ice dynamics

Identification of a lysine residue in the NADH-Binding site of salicylate hydroxylase from Pseudomonas putida S-1

金沢大学自然科学研究科　　金沢大学理工研究域自然システム学系Salicylate hydroxylase from Pseudomonas putida S-1 was irreversibly inactivated by trinitrobenzenesulfonic acid (TNBS). The reaction was linearly dependent on TNBS concentration and the second-order rate constant was 120 M-1.min-1 for the holoprotein at pH 8.5. Modification of one mole of lysine residue per mole of enzyme caused a large loss of the activity, and the enzyme was no longer able to show NADH-dehydrogenase activity after uncoupling. The presence of NADH, NAD+, ATP, or AMP afforded protection against the inactivation. The enzyme modified at a single lysine residue was isolated by hydrophobic chromatagraphy as an apoprotein form and characterized. It could bind FAD with the same K(d) value for that of native apoprotein. The apparent Michaelis constant of the enzyme was increased 13-fold for NADH, but not for salicylate. V(max) for NADH oxidation was decreased to one-fifth of that of the native enzyme. A peptide containing one trinitrophenyl-lysine residue was isolated from the chymotryptic digest of the modified enzyme and its amino acid sequence was determined to be TADVAIAADGIKSSM, which is homologous to the sequence from R-154 to I-168 of salicylate hydroxylase from P, putida PpG7. The lysine in the peptide may represent a basic residue interacting with an anionic group of NADH in the binding site of the enzyme