Disease relevance of mak

• The mak gene was located at min 8.8 on the E. coli linkage map as an ORF designated yajF, of hitherto unknown function; it specifies a deduced polypeptide of 344 aa [1].
• Cloning, sequencing, and expression of the Zymomonas mobilis fructokinase gene and structural comparison of the enzyme with other hexose kinases [2].
• Bifidobacterium longum requires a fructokinase (Frk; ATP:D-fructose 6-phosphotransferase, EC 2.7.1.4) for fructose catabolism [3].
• Of the five chromosome-located fragments, three were predicted to encode parts of proteins that were significantly homologous to previously described proteins: TktA (transketolase) of Haemophilus influenzae, a FruA (fructokinase) homologue of Listeria innocua and Gp2 (large terminal subunit) of phage 21 [4].
• A gene encoding a phosphomannose isomerase from Streptococcus mutans GS-5 was identified immediately downstream from the fructokinase gene, scrK [5].

High impact information on mak

• The latter is phosphorylated by an ATP-dependent fructokinase (gene scrK of an scr regulon) to D-fructose 6-phosphate [6].
• Gene scrK apparently codes for an intracellular and ATP-dependent fructokinase (39 kD), while scrY seems to code for a sucrose porin (58 kD) in the outer cell membrane [7].
• Under these conditions, the bacterium acquires a spontaneous mutation in the putative promoter region of the yajF gene, a locus previously shown to encode a sugar kinase with relaxed substrate specificity [8].
• The point mutation regenerates a consensus sigma(70) promoter sequence that leads to a 94-fold increase in the level of yajF expression [8].
• The B. longum A10C fructokinase-encoding gene (frk) was expressed in Escherichia coli from a pET28 vector with an attached N-terminal histidine tag [3].

Biological context of mak

• The frk gene encoding the enzyme fructokinase (fructose 6-phosphotransferase [EC 2.7.1.4]) from Zymomonas mobilis has been isolated on a partial TaqI digest fragment of the genome and sequenced [2].
• Comparison of the amino acid sequence with that of the glucokinase enzyme (EC 2.7.1.2) from Z. mobilis reveals relatively little homology, despite the fact that fructokinase also binds glucose and has kinetic and structural properties similar to those of glucokinase [2].
• The gene encoding fructokinase (EC 2.7.1.4) from Zymomonas mobilis has been expressed at high level in Escherichia coli by modifying the ribosome binding site using the polymerase chain reaction [9].

Associations of mak with chemical compounds

• Recombinant cells of different Z. mobilis strains utilized mannose (4%) as the sole carbon source with a growth rate of 0.07 h-1, provided that they contained fructokinase activity [10].
• Moreover, D-mannose was phosphorylated by a side activity of the resident fructokinase to mannose-6-phosphate [10].
• Molecular and biochemical characterization of a fructose-6-phosphate-forming and ATP-dependent fructokinase of the hyperthermophilic archaeon Thermococcus litoralis [11].

Analytical, diagnostic and therapeutic context of mak

• Using the polymerase chain reaction in mutagenic conditions, a variant of fructokinase was isolated which was more thermostable than the wild type, taking the 30 min half-life from 70.1 to 72.4 degrees C. The purified thermostable variant had the same specific activity as the wild type [9].

References