Lindner Steffen N, Vidaurre Dolores, Willbold Sabine, Schoberth Siegfried M, Wendisch Volker F
Institute of Molecular Microbiology and Biotechnology, Westfalian Wilhelms University Muenster, Correnstr. 3, Muenster, Germany.
Appl Environ Microbiol. 2007 Aug;73(15):5026-33. doi: 10.1128/AEM.00600-07. Epub 2007 Jun 1.
Corynebacterium glutamicum is able to accumulate up to 600 mM cytosolic phosphorus in the form of polyphosphate (poly P). Granular poly P (volutin) can make up to 37% of the internal cell volume. This bacterium lacks the classic enzyme of poly P synthesis, class I polyphosphate kinase (PPK1), but it possesses two genes, ppk2A (corresponds to NCgl0880) and ppk2B (corresponds to NCgl2620), for putative class II (PPK2) PPKs. Deletion of ppk2B decreased PPK activity and cellular poly P content, while overexpression of ppk2B increased both PPK activity and cellular poly P content. Neither deletion nor overexpression of ppk2A changed specific activity of PPK or cellular poly P content significantly. Purified PPK2B of C. glutamicum is active as a homotetramer and formed poly P with an average chain length of about 125, as determined with (31)P nuclear magnetic resonance. The catalytic efficiency of C. glutamicum PPK2B was higher in the poly P-forming direction than for nucleoside triphosphate formation from poly P. The ppk2B deletion mutant, which accumulated very little poly P and grew as C. glutamicum wild type under phosphate-sufficient conditions, showed a growth defect under phosphate-limiting conditions.
谷氨酸棒杆菌能够以多聚磷酸盐（多聚P）的形式在胞质中积累高达600 mM的磷。颗粒状多聚P（异染粒）可占细胞内体积的37%。这种细菌缺乏多聚P合成的经典酶，即I类多聚磷酸激酶（PPK1），但它拥有两个假定的II类（PPK2）多聚磷酸激酶的基因，ppk2A（对应于NCgl0880）和ppk2B（对应于NCgl2620）。缺失ppk2B会降低PPK活性和细胞内多聚P含量，而ppk2B的过表达则会增加PPK活性和细胞内多聚P含量。ppk2A的缺失或过表达均未显著改变PPK的比活性或细胞内多聚P含量。经纯化的谷氨酸棒杆菌PPK2B作为同四聚体具有活性，通过（31）P核磁共振测定，其形成的多聚P平均链长约为125。谷氨酸棒杆菌PPK2B在多聚P形成方向上的催化效率高于从多聚P形成核苷三磷酸的催化效率。ppk2B缺失突变体在磷酸盐充足的条件下积累的多聚P极少，生长情况与谷氨酸棒杆菌野生型相同，但在磷酸盐限制条件下表现出生长缺陷。
