A novel sucrose hydrolase (SUH) from Xanthomonas axonopodis pv. glycines, a causative agent of bacterial pustule disease on soybeans, was studied at the functional and molecular levels. SUH was shown to act rather specifically on sucrose (K m ‫؍‬ 2.5 mM) but not on sucrose-6-phosphate. Protein analysis of purified SUH revealed that, in this monomeric enzyme with an estimated molecular mass of 70,223 ؎ 12 Da, amino acid sequences determined for several segments have corresponding nucleotide sequences in XAC3490, a proteincoding gene found in the genome of X. axonopodis pv. citri. Based on this information, the SUH gene, consisting of an open reading frame of 1,935 bp, was cloned by screening a genomic library of X. axonopodis pv. glycines 8ra. Database searches and sequence comparison revealed that SUH has significant homology to some family 13 enzymes, with all of the crucial invariant residues involved in the catalytic mechanism conserved, but it shows no similarity to known invertases belonging to family 32. suh expression in X. axonopodis pv. glycines requires sucrose induction, and insertional mutagenesis resulted in an absence of sucrose-inducible sucrose hydrolase activity in crude protein extracts and a sucrose-negative phenotype. Recombinant SUH, overproduced in Escherichia coli and purified, was shown to have the same enzymatic characteristics in terms of kinetic parameters.Plant-pathogenic bacteria grow in the intercellular spaces of plant tissues, relying on nutrients available there. In higher plants, sucrose (␣-D-glucopyranosyl ␤-D-fructofuranoside) is the major transportable product of photosynthesis that flows from the source organs to the sink organs. The process of the source-sink flow involves phloem loading, for which sucrose has to exit from the mesophyll cell, and from the apoplasm, it enters the phloem. Sucrose is naturally the predominant form of carbohydrate found in the intercellular spaces of photosynthetically active tissues. Pathogens with their habitats in mature leaves, therefore, may utilize sucrose as the main, if not the only, source for carbon and energy and possess systems for a sucrose utilization pathway. Nevertheless, information on such systems in plant-associated bacteria is rather scanty. To our knowledge, Erwinia amylovora, the causative agent for fire blight of rosaceous plants, is the only phytopathogen that has been studied at the molecular level in relation to sucrose utilization (4).Many sucrose-positive bacteria have a phosphoenolpyruvate-dependent, sucrose-specific phosphotransferase system (PTS) that promotes sucrose translocation across the cytoplasmic membrane with concomitant phosphorylation (27, 28). The resulting intracellular sucrose-6-phosphate (S-6-P) is then hydrolyzed by S-6-P hydrolase to yield D-glucose-6-phosphate and D-fructose. In some bacteria, however, sucrose itself can be transported into the cytoplasm without phosphorylation via a pathway independent of PTS. For instance, the Escherichia coli strain EC3132, which is able to grow on sucrose, be...

Forty-three glucocorticoids in deceptively advertised cosmetic products from the online or offline market are detected and determined through a validated simultaneous detection method based on LC-MS/MS.