Different glycolytic pathways for glucose and fructose in the halophilic archaeon Halococcus saccharolyticus

Citation
U. Johnsen et al., Different glycolytic pathways for glucose and fructose in the halophilic archaeon Halococcus saccharolyticus, ARCH MICROB, 175(1), 2001, pp. 52-61
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ARCHIVES OF MICROBIOLOGY
ISSN journal
0302-8933 → ACNP
Volume
175
Issue
1
Year of publication
2001
Pages
52 - 61
Database
ISI
SICI code
0302-8933(200101)175:1<52:DGPFGA>2.0.ZU;2-U
Abstract
The glucose and fructose degradation pathways were analyzed in the halophil ic archaeon Halococcus saccharolyticus by C-13-NMR labeling studies in grow ing cultures, comparative enzyme measurements and cell suspension experimen ts. H. saccharolyticus grown on complex media containing glucose or fructos e specifically C-13-labeled at C1 and C3, formed acetate and small amounts of lactate. The C-13-labeling patterns, analyzed by H-1- and C-13-NMR, indi cated that glucose was degraded via an Entner-Doudoroff (ED) type pathway ( 100%), whereas fructose was degraded almost completely via an Embden-Meyerh of (EM) type pathway (96%) and only to a small extent (4%) via an ED pathwa y. Glucose-grown and fructose-grown cells contained all the enzyme activiti es of the modified versions of the ED and EM pathways recently proposed for halophilic archaea. Glucose-grown cells showed increased activities of the ED enzymes gluconate dehydratase and 2-keto-3-deoxy-gluconate kinase, wher eas fructose-grown cells contained higher activities of the key enzymes of a modified EM pathway, ketohexokinase and fructose-1-phosphate kinase. Duri ng growth of H. saccharolyticus on media containing both glucose and fructo se, diauxic growth kinetics were observed. After complete consumption of gl ucose, fructose was degraded after a lag phase, in which fructose-1-phospha te kinase activity increased. Suspensions of glucose-grown cells consumed i nitially only glucose rather than fructose, those of fructose-grown cells d egraded fructose rather than glucose. Upon longer incubation times, glucose - and fructose-grown cells also metabolized the alternate hexoses. The data indicate that, in the archaeon H. saccharolyticus, the isomeric hexoses gl ucose and fructose are degraded via inducible, functionally separated glyco lytic pathways: glucose via a modified ED pathway, and fructose via a modif ied EM pathway.