Fructose Transport in Bacillus subtilis

Abstract

The transport of fructose in Bacillus subtilis was studied in various mutant strains lacking the following activities : ATP-dependent fructokinase CfruC), the fructose 1-phosphate kinase WruB) the phosphofructokinase kjk), the enzyme I of the phosphoenolpyruvate phosphotransferase system (the thermosensitive mutationptsll), and a transport activity CfruA). Combinations of these mutations indicated that the transport of fructose in Bacillus subtilis is tightly coupled to its phosphorylation either in fructose 1-phosphate, identified in vivo and in vitro or in fructose 6-phosphate identified by indirect lines of evidence. These steps of fructose metabolism were shown to depend on the activity of the enzyme I of the phosphoenolpyruvate phosphotransferase systems.The fruA mutations affect the transport of fructose when the bacteria are submitted to catabolite repression. The mutations were localized on the chromosome of Bacillus subtilis in a cluster including the fruB gene. When grown in a medium supplemented by a mixture of potassium glutamate and succinate the fruA mutants are able to carry on the two vectorial metabolisms generating fructose 6-phosphate as well as fructose 1-phosphate. A negative search of strictly negative transport mutants in fruA strains indicated that more than two structural genes are involved in the transport of fructose.In a wide range of bacteria including Aerobacter aerogenes [1], Bacterioides syrnbiosus [2], Escherichia coli [3], fructose catabolism was described to follow the fructose 1-phosphate pathway. The main characteristic of this route is the existence of the so-called vectorial metabolism step, i.e. a phosphorylation tightly coupled to the transport, catalysed by a phosphoenolpyruvate-dependent phosphotransferase system first described by Kundig et al. [4] (for recent review see [5]). An extensive study of the fructose metabolism and transport in Escherichia coli was completed by H. L. Kornberg and co-workers. Using various combinations of mutations blocking either the fructose 6-phosphate metabolism or the fructose 1-phosphate metabolism, Ferenci and Kornberg [6] obtained evidence for a second vectorial metabolism leading to fructose 6-phosphate. The genetic study was achieved by the isolation/of transport mutants affected in each system (Jones-Mortimer and Kornberg [7]) and of mutants affected in the regulation of the fructose transport (Amaral and Kornberg [S]).Some mutations affecting fructose metabolism have been previously described in Bacillus subtilis (see Abbreviation. HPr protein, histidine-containing phosphocarrier protein of the phosphoennlpyruvate-dependent phosphotransferase system. Tables 1 and 2), they included fruB affecting the fructose 1-phosphate kinase activity [9], fruC affecting the ATP-dependent fructokinase [lo], ptsl affecting the activity of the enzyme I of the phosphoenolpyruvate phosphotransferase system [ l l , 121 and the fruA mutation affecting the fructose transport [13]. A genetic localization of these mutations on the Bacillus subtilis chrom...

Identification of a phosphoenolpyruvate:fructose phosphotransferase system (fructose-1-phosphate forming) in Listeria monocytogenes

“…The former activity was comparable to activities found in fructose-grown B. subtilis (5) and Streptococcus mutans (4). The results establish that L. monocytogenes contains a fructose-i-P-forming PEP:fructose PTS as well as fructose-i-P kinase.…”

The Bacillus subtilis ywjI ( glpX ) Gene Encodes a Class II Fructose-1,6-Bisphosphatase, Functionally Equivalent to the Class III Fbp Enzyme

“…We also tested fructose, which is mainly transported and phosphorylated in fructose-1-phosphate via the FruA phosphotransferase system fructose-specific enzyme IIABC to enter glycolysis, after phosphorylation by the FruK fructose-1-phosphate kinase, as fructose-1,6-bisphosphate (9). Therefore, with respect to the synthesis of fructose-6-phosphate, most of the fructose represents a "gluconeogenic" substrate.…”

The Q15H mutation enables Crh, a Bacillus subtilis HPr-like protein, to carry out some regulatory HPr functions, but does not make it an effective phosphocarrier for sugar transport

“…However, fructose uptake via the lev-PTS is very slow (Gay & Delobbe, 1973 ;Martin-Verstraete et al, 1990). Although the lev-PTS is fully active in fruA or fruB mutants, which are defective in enzyme IIA Fru or phosphofructokinase 1, respectively, two components of the main fructose metabolic pathway in B. subtilis, doubling times exceeding 360 min have been reported for these mutants when they were grown on fructose as the sole carbon source (Gay & Delobbe, 1973). This low fructose-transport activity of the lev-PTS explains why the synthesis of CrhQ15H did not restore growth of a ptsH mutant on fructose (Table 1), although the mutant Crh was found to phosphorylate LevD (Fig.…”