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PubMed1991

Separation and characterization of three positional isomers of dimaltosyl-cyclomaltoheptaose (dimaltosyl-beta-cyclodextrin).

A mixture of maltosylcyclomaltoheptaoses (maltosyl-beta-cyclodextrins, G2-beta CDs) was prepared from maltose and beta-cyclodextrin (beta CD) through the reverse action of Klebsiella pneumoniae pullulanase. Three positional isomers of dimaltosyl-beta CD in the mixture were separated by high-performance liquid chromatography on a reversed phase column and a graphitized carbon column. Their molecular weights were measured by fast-atom bombardment mass spectrometry, and the structures were established by methylation analysis, hydrolysis with glucoamylase to the known compounds, three positional isomers of diglucosyl-beta CD, and 13C-nuclear magnetic resonance spectroscopy.

Cyclodextrins↗
PubMed1998

Some properties and the inclusion behavior of three positional isomers of 6(1),6n-di-O-alpha-D-glucosyl-cyclomaltoheptaoses (beta-cyclodextrins).

Three positional isomers of 6(1),6n-di-O-alpha-D-glucosyl-cyclomaltoheptaose [1,n-(G)2-beta CDs; n = 2-4] which existed in the digests with glucoamylase of the products from cyclomaltoheptaose (beta-cyclodextrin, beta CD) and maltose with Klebsiella pneumoniae pullulanase, were purified by HPLC. The solubilities of two isomers of those doubly branched beta CDs, 1,2- and 1,3-(G)2-beta CDs, in water were much higher than those of parent non-branched beta CD and mono-branched beta CD, 6-O-alpha-D-glucosyl-beta CD (G-beta CD), while the solubility of another isomer, 1,4-(G)2-beta CD, was significantly lower than these two isomers, though it was higher than that of beta CD. On the other hand, the solubilities of 1,2- and 1,3-isomers in 10, 30, and 50% (v/v) aqueous methanol at 25 degrees C were independent of methanol concentrations and their solubilities were the same as those in water at 25 degrees C. However, that of 1,4-isomer increased with increasing methanol concentrations. The hemolytic activities of 1,n-(G)2-beta CDs on human erythrocytes in isotonic solution were lower than those of G-beta CD and beta CD, and became weaker in the order of 1,4- > 1,2- > 1,3-isomers. The complex-forming abilities of 1,n-(G)2-beta CDs for digitoxin, digoxin, fluorometholone, flurbiprofen, hydrocortisone acetate, and norfloxacin were about the same as those of beta CD and G-beta CD, whereas reserpine was more difficult to include within 1,n-(G)2-beta CDs than beta CD and G-beta CD. Nevertheless, the solubilities of those guest compounds were much more enhanced by 1,n-(G)2-beta CDs and G-beta CD than by beta CD.

Chemical Phenomena↗
PubMed2000

[Biological activities of natural resources around us are now in the limelight].

There are various kind of natural resources around us, and they must contain a lot of unknown bioactive substances. Some may be structurally very strange for us, and some are very familiar. But their biological activity was not unfortunately investigated in detail. Accordingly, exploring new types of pharmaceutical resources may give lead compounds of the drugs in the future. Among those natural resources, I examined squid ink and scallop soup. From squid ink, an antitumor glycoconjugate was obtained. Its polysaccharide moieties, illexin A, illexin B and illexin C, were isolated, and the spectral data and chemical transformation of their acid hydrolysate revealed to bear a unique branched repeating unit, [-3GlcA beta 1-4(GalNAc alpha 1-3)Fuc alpha 1-]n. Moreover, scallop soup gave antitumor glycogen by the action of protease. The fine structure of glycogen was investigated by the sequential enzyme digestion method using beta-amylase and pullulanase, while the unit chain was analyzed by high performance anion exchange chromatography. The results showed that the antitumor active glycogen was highly branched with shorter chain than glycogens without antitumor activity.

Animals↗
PubMed1996

Extracellular production of a Serratia marcescens serine protease in Escherichia coli.

The Serratia marcescens serine protease (SSP) is one of the extracellular enzymes secreted from this Gram-negative bacterium. When the ssp gene, which encodes a SSP precursor (preproSSP) composed of a typical NH2-terminal signal peptide, a mature enzyme domain, and a large COOH-terminal pro-region, is expressed in Escherichia coli, the mature protease is excreted through the outer membrane into the medium. The COOH-terminal pro-region, which is integrated into the outer membrane, provides the essential function for the export of the mature protein across the outer membrane. This is a very simple pathway, in contrast to the general secretory pathway exemplified by the secretion of a pullulanase from Klebsiella oxytoca, in which many separately encoded accessory proteins are required for the transport through the outer membrane. Moreover, the NH2-terminal region of 71 amino acid residues of the COOH-terminal pro-sequence plays an essential role, as an "intramolecular chaperone," in the folding of the mature enzyme in the medium. In addition to ssp, the S. marcescens strain contains two ssp homologues encoding proteins similar to SSP in amino acid sequence and size, but with no protease activity. Characterization of the homologue proteins and chimeric proteins between the homologues and SSP, all of which are produced in E. coli, has shown that they are membrane proteins that are localized in the outer membrane in the same manner as for SSP. By use of the COOH-terminal domain of SSP, pseudoazurin was exported to the cell surface of E. coli, which proves the usefulness of the SSP secretory system in the export of foreign proteins across the outer membrane.

Biological Transport↗
PubMed1996

Separation of functional domains for the alpha-1,4 and alpha-1,6 hydrolytic activities of a Bacillus amylopullulanase by limited proteolysis with papain.

An amylopullulanase (APase) from alkalophilic Bacillus sp. KSM-1378 hydrolyzes both alpha-1,6 linkages in pullulan and alpha-1,4 linkages in other polysaccharides, each maximally active at an alkaline pH, to generate oligosaccharides. We analyzed proteolytic fragments that were produced by exposing pure APase to various proteases, to identify its catalytic domain(s). The intact, pure 210-kDa APase was partially digested with papain for a short time, yielding simultaneously two smaller non-overlapping active fragments, designated amylose-hydrolyzing fragment (AHF114, 114 kDa) and pullulan-hydrolyzing fragment (PHF102, 102 kda). The two truncated protein fragments, each containing a single catalytic domain, were purified to homogeneity. The purified AHF114 and PHF102 had similar enzymatic properties to the amylase and pullulanase activities, respectively, of intact APase. The partial amino-terminal sequences of APase and AHF114 were both Glu-Thr-Gly-Asp-Lys-Arg-Ile-Glu-Phe-Ser-Tyr-Glu-Arg-Pro and that of PHF102 was Thr-Val-Pro-Leu-Ala-Leu-Val-Ser-Gly-Glu-Val-Leu-Ser-Asp-Lsy-Leu. These results were direct evidence that the alpha-1,6 and alpha-1,4 hydrolytic activities were associated with two different active sites in this novel enzyme. Our alkaline APase is obviously a "biheaded enzyme".

Amino Acid Sequence↗
PubMed2005

Synthesis of novel heterobranched beta-cyclodextrins having beta-D-N-acetylglucosaminyl-maltotriose on the side chain.

From a mixture of N-acetylglucosaminyl-beta-cyclodextrin (GlcNAc-betaCD) and lactose, beta-D-galactosyl-GlcNAc-betaCD (Gal-GlcNAc-betaCD) was synthesized by the transfer action of beta-galactosidase. GlcNAc-maltotriose (Glc3) and Gal-GlcNAc-Glc3 were produced with hydrolysis of GlcNAc-betaCD by cyclodextrin glycosyltransferase, and Gal-GlcNAc-betaCD by bacterial saccharifying alpha-amylase respectively. Finally, GlcNAc-Glc3-betaCD and Gal-GlcNAc-Glc3-betaCD were synthesized in 5.2% and 3.5% yield when Klebsiella pneumoniae pullulanase was incubated with the mixture of GlcNAc-Glc(3) and betaCD, or Gal-GlcNAc-Glc3 and betaCD respectively. The structures of GlcNAc-Glc3-betaCD and Gal-GlcNAc-Glc3-betaCD were analyzed by FAB-MS and NMR spectroscopy and identified as 6-O-alpha-(6(3)-O-beta-D-N-acetylglucosaminyl-maltotriosyl)-betaCD, and 6-O-alpha-(4-O-beta-D-galactopyranosyl-6(3)-O-beta-D-N-acetylglucosaminyl-maltotriosyl)-betaCD respectively.

Carbohydrate Sequence↗
PubMed2001

Thermozymes and their applications: a review of recent literature and patents.

Enzymes from thermophilic microorganisms, thermozymes, have unique characteristics such as temperature, chemical, and pH stability. They can be used in several industrial processes, in which they replace mesophilic enzymes or chemicals. Thermozymes are often used when the enzymatic process is compatible with existing (high-temperature) process conditions. The main advantages of performing processes at higher temperatures are reduced risk of microbial contamination, lower viscosity, improved transfer rates, and improved solubility of substrates. However, cofactors, substrates, or products might be unstable or other side reactions may occur. Recent developments show that thermophiles are a good source of novel catalysts that are of great industrial interest. Thermostable polymer-degrading enzymes such as amylases, pullulanases, xylanases, proteases, and cellulases are expected to play an important role in food, chemical, pharmaceutical, paper, pulp, and waste-treatment industries. Considerable research efforts have been made to better understand the stability of thermozymes. There are no major conformational differences with mesophilic enzymes, and a small number of extra salt bridges, hydrophobic interactions, or hydrogen bounds seem to confer the extra degree of stabilization. Currently, overexpression of thermozymes in standard Escherichia coli allows the production of much larger quantities of enzymes, which are easy to purify by heat treatment. With wider availability and lower cost, thermophilic enzymes will see more application in industry.

Archaea↗
PubMed2002

Production and characterization of pullulan from beet molasses using a nonpigmented strain of Aureobasidium pullulans in batch culture.

The production of pullulan from beet molasses by a pigment-free strain of Aztreobasidium pullulans on shake-flask culture was investigated. Combined pretreatment of molasses with sulfuric acid and activated carbon to remove potential fermentation inhibitors present in molasses resulted in a maximum pullulan concentration of 24 g/L, a biomass dry wt of 14 g/L, a pullulan yield of 52.5%, and a sugar utilization of 92% with optimum fermentation conditions (initial sugar concentration of 50 g/L and initial pH of 7.0). The addition of other nutrients as carbon and nitrogen supplements (olive oil, ammonium sulfate, yeast extract) did not further improve the production of the exopolysaccharides. Structural characterization of the isolated polysaccharides from the fermentation broths by 13C-nuclear magnetic resonance spectroscopy and pullulanase digestion combined with size-exclusion chromatography confirmed the identity of pullulan and the homogeneity (>93% dry basis) of the elaborated polysaccharides by the microorganism. Using multiangle laser light scattering and refractive index detectors in conjunction with high-performance size-exclusion chromatography molecular size distributions and estimates of the molecular weight (Mw = 2.1-4.1 x 10(5)), root mean square of the radius of gyration (R = 30-38 nm), and polydispersity index (Mw/Mn = 1.4-2.4) were obtained. The fermentation products of molasses pretreated with sulfuric acid and/or activated carbon were more homogeneous and free of contaminating proteins. In the concentration range of 2.8-10.0 (w/v), the solution's rheologic behavior of the isolated pullulans was almost Newtonian (within 1 and 1200 s(-1) at 20 degrees C); a slight shear thinning was observed at 10.0 (w/v) for the high molecular weight samples. Overall, beet molasses pretreated with sulfuric acid and activated carbon appears as an attractive fermentation medium for the production of pullulan by A. pullulans.

Ascomycota↗
PubMed1987

Recent advances in Bacteroides genetics.

Bacteroides are Gram-negative, obligate anaerobes that are present in high concentrations within the intestinal tracts of humans and animals. Bacteroides are also important opportunistic pathogens of humans and animals. Methods for genetic manipulation of these important organisms have only recently begun to emerge. Shuttle vectors which can be transferred by conjugation between Escherichia coli to Bacteroides are now available. A method for transforming some strains of Bacteroides has been developed. Two Bacteroides transposons, Tn4351 and Tn4400, have been found and one of them, Tn4351, has been used for transposon mutagenesis of Bacteroides. Several different Bacteroides genes have now been cloned, including a gene that codes for resistance to clindamycin, genes that code for polysaccharidases (chondroitin lyase and pullulanase), and a gene that codes for a fimbrial subunit. These cloned genes have been used to study the organization and regulation of Bacteroides genes.

Animals↗
PubMed1991

The glucoamylase multigene family in Saccharomyces cerevisiae var. diastaticus: an overview.

Saccharomyces cerevisiae has been used widely both as a model system for unraveling the biochemical, genetic, and molecular details of gene expression and the secretion process, and as a host for the production of heterologous proteins of biotechnological interest. The potential of starch as a renewable biological resource has stimulated research into amylolytic enzymes and the broadening of the substrate range of S. cerevisiae. The enzymatic hydrolysis of starch, consisting of linear (amylose) and branched glucose polymers (amylopectin), is catalyzed by alpha- and beta-amylases, glucoamylases, and debranching enzymes, e.g., pullulanases. Starch utilization in the yeast S. cerevisiae var. diastaticus depends on the expression of the three unlinked genes, STA1 (chr. IV), STA2 (chr. II), and STA3 (chr. XIV), each encoding one of the extracellular glycosylated glucoamylases isozymes GAI, GAII, or GAIII, respectively. The restriction endonuclease maps of STA1, STA2, and STA3 are identical. These genes are absent in S. cerevisiae, but a related gene, SGA1, encoding an intracellular, sporulation-specific glucoamylase (SGA), is present. SGA1 is homologous to the middle and 3' regions of the STA genes, but lacks a 5' sequence that encodes the domain for secretion of the extracellular glucoamylases. The STA genes are positively regulated by the presence of three GAM genes. In addition to positive regulation, the STA genes are regulated negatively at three levels. Whereas strains of S. diastaticus are capable of expressing the STA genes, most strains of S. cerevisiae contain STA10, whose presence represses the expression of the STA genes in an undefined manner. The STA genes are also repressed in diploid cells, presumably by the MATa/MAT alpha-encoded repressor. STA gene expression is reduced in liquid synthetic media, it is carbon catabolite repressed by glucose, and is inhibited in petite mutants.

Base Sequence↗
PubMedDate not supplied

Measurement of total fructan in foods by enzymatic/spectrophotometric method: collaborative study.

An AOAC collaborative study was conducted to evaluate the accuracy and reliability of an enzyme assay kit procedure for measuring oligofructans and fructan polysaccharide (inulins) in mixed materials and food products. The sample is extracted with hot water, and an aliquot is treated with a mixture of sucrase (a specific sucrose-degrading enzyme), alpha-amylase, pullulanase, and maltase to hydrolyze sucrose to glucose and fructose, and starch to glucose. These reducing sugars are then reduced to sugar alcohols by treatment with alkaline borohydride solution. The solution is neutralized, and excess borohydride is removed with dilute acetic acid. The fructan is hydrolyzed to fructose and glucose using a mixture of purified exo- and endo-inulinanases (fructanase mixture). The reducing sugars produced (fructose and glucose) are measured with a spectrophotometer after reaction with para-hydroxybenzoic acid hydrazide. The samples analyzed included pure fructan, chocolate, low-fat spread, milk powder, vitamin tablets, onion powder, Jerusalem artichoke flour, wheat stalks, and a sucrose/cellulose control flour. Repeatability relative standard deviations ranged from 2.3 to 7.3%; reproducibility relative standard deviations ranged from 5.0 to 10.8%.

Borohydrides↗
PubMed2001

Biochemical and genetic analysis of the effects of amylose-extender mutation in rice endosperm.

Biochemical analysis of amylose-extender (ae) mutant of rice (Oryza sativa) revealed that the mutation in the gene for starch-branching enzyme IIb (BEIIb) specifically altered the structure of amylopectin in the endosperm by reducing short chains with degree of polymerization of 17 or less, with the greatest decrease in chains with degree of polymerization of 8 to 12. The extent of such change was correlated with the gelatinization properties of the starch granules, as determined in terms of solubility in urea solution. The ae mutation caused a dramatic reduction in the activity of BEIIb. The activity of soluble starch synthase I (SSI) in the ae mutant was significantly lower than in the wild type, suggesting that the mutation had a pleiotropic effect on the SSI activity. In contrast, the activities of BEI, BEIIa, ADP-Glc pyrophosphorylase, isoamylase, isoamylase, pullulanase, and Suc synthase were not affected by the mutation. Therefore, it is stressed that the function of BEIIb cannot be complemented by BEIIa and BEI. These results strongly suggest that BEIIb plays a specific role in the transfer of short chains, which might then be extended by SS to form the A and B(1) chains of amylopectin cluster in rice endosperm.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1975

[An intracellular polysaccharide involved in sporulation of "Clostridium butyricum" I. Cytology, production and preliminary enzymic analysis (author's transl)].

Free glucose concentration and polysaccharide production in Clostridium butyricum cells have been studied with an enzymatic method. Results indicated a substantial decrease in intracellular glucose content simultaneously with a production of polysaccharide prior to the end of exponential growth. Then the polysaccharide accumulated rapidly to reach a maximum just before the first refractile spores appeared, and it decreased by 50% during the last stages (V and VI) of sproulation. Electron micrographs of ultrathin sections have demonstrated that most of the polysaccharide is located inside the mother cell cytoplasm as large granules when the remaining is dispersed within the spore cytoplasm beginning during stage III of the sporulation. Overall results showed that production and use of C. butyricum polysaccharide were closely related to sporulation. The isolated polysaccharide exhibited poor water solubility, iodine spectrum with a lambda max at 545 nm and 72% beta-amylolysis. Total hydrolysis occurred with amyloglucosidase indicating an alpha-glucan containing alpha(1 leads to 4) and alpha(1 leads to 6) glucose linkages. The debranching from its beta-dextrin limit by pullulanase revealed the presence of a glycogen like-type structure with some external chains which are longer than those of a normal glycogen. This glycogen arrangement appeared to be of clusters linked by linear chains at least as long as the longest external chains.

Clostridium↗
PubMed2002

Laboratory scale production of maltodextrins and glucose syrup from banana starch.

Banana starch was isolated to obtain maltodextrin by enzymatic hydrolysis with a heat-stable alpha-amylase. The maltodextrin obtained had a dextrose equivalent (DE) between 7-11 and showed suitable chemical characteristics for food application. Additionally, banana maltodextrin had a greater white color value and total color difference (delta E) than a sample of commercial maltodextrin. Further saccharification of the maltodextrins was carried out with amyloglucosidase and pullulanase at 60 degrees C during 24 h obtaining a glucose syrup. Chemical characteristics of banana glucose syrup were compared with those of a commercial syrup obtaining similar results. Nevertheless, the color of banana glucose syrup was clearer than the one of a sample of commercial syrup. However, it showed lower color stability than the commercial sample, i.e., the color of banana glucose syrup changed as a function of storage time. Banana starch may be used to obtain maltodextrins and glucose syrups with similar chemical characteristics of those obtained from maize starch. Particularly, the color of banana maltodextrin is adequate for its use in food products.

Glucose↗
PubMed1990

Structure of di-O-alpha-maltosyl cyclodextrins produced from alpha-maltosylfluoride and cyclodextrins.

The structures of di-O-alpha-maltosyl beta-cyclodextrins ((G2)2-beta-CDs), which were produced from alpha-maltosylfluoride (alpha-G2F) and cyclodextrin (CD) by the transfer action of debranching enzymes, were examined by the enzymic method using Bacillus subtilis saccharifying alpha-amylase (BSA). (G2)2-beta-CD was converted to (G1)2-beta-CD by treatment with glucoamylase before the examination. BSA completely hydrolyzed (G1)2-beta-CD to produce glucose, 6(3)-O-alpha-glucosylmaltotriose, and 6(3),6(5)-di-O-alpha-glucosyl maltopentaose. (G2)2-beta-CD was the mixture of 6A,6C-di-O-alpha-maltosyl beta-CD and 6A,6D-di-O-alpha-maltosyl beta-CD. The ratio of A,C/A,D in (G2)2-beta-CD synthesized with Pseudomonas isoamylase and Aerobacter pullulanase were 40:60-45:55 and 30:70, respectively. The content of 6A,6C-di-O-alpha-maltosyl gamma-CD in (G2)2-gamma-CD synthesized by isoamylase was about 35%.

Bacillus subtilis↗
PubMed1991

Enzymic production of sweet stevioside derivatives: transglucosylation by glucosidases.

For the purpose of improving sweetness and a further study on the structure-sweetness relationship of steviol glycosides, transglycosylation of stevioside by a variety of commercial glucosidases was investigated. It was revealed that two alpha-glucosidases gave glucosylated products. Transglucosylation of stevioside by Pullulanase and pullulan exclusively afforded three products, 13-O-[beta-maltotriosyl-(1----2)-beta-D-glucosyl]-19-O-beta-D-g luc osyl- steviol (1), 13-O-[beta-maltosyl-(1----2)-beta-D-glucosyl]-19-O-beta-D-glucosyl- steviol (2) and 13-O-beta-sophorosyl-19-O-beta-maltotriosyl-steviol (3). All of these products have already been obtained by trans-alpha-1,4-glucosylation of stevioside by the cyclodextrin glucanotransferase starch system, and 1 and 2 have been proven to be tasty and potent sweeteners. Transglucosylation of stevioside by Biozyme L and maltose afforded three new products, 4, 5 and 6, the structures of these compounds being elucidated as 13-O-beta-sophorosyl-19-O-beta-isomaltosyl-steviol (4), 13-O-[beta-isomaltosyl(1----2)-beta-D-glucosyl]-19-O-beta-D-glucosyl- steviol (5) and 13-O-[beta-nigerosyl-(1----2)-beta-D-glucosyl]-19-O-beta-D- glucosyl-steviol (6). A significantly high quality of taste was evaluated for 4.

Carbohydrate Sequence↗
PubMed1992

Action of neopullulanase. Neopullulanase catalyzes both hydrolysis and transglycosylation at alpha-(1----4)- and alpha-(1----6)-glucosidic linkages.

The transglycosylation reaction catalyzed by neopullulanase was analyzed. Radioactive oligosaccharides were produced when the enzyme acted on maltotriose in the presence of [U-14C]glucose. Some of the radioactive oligosaccharides had only alpha-(1----4)-glucosidic linkages, but others were suggested to have alpha-(1----6)-glucosidic linkages. The existence of alpha-(1----6)-glucosidic linkages in the products from maltotriose with neopullulanase was proven by proton NMR spectroscopy and methylation analysis. We previously reported that the one active center of neopullulanase catalyzes the hydrolysis of alpha-(1----4)- and alpha-(1----6)-glucosidic linkages (Kuriki, T., Takata, H., Okada, S., and Imanaka, T. (1991) J. Bacteriol. 173,6147-6152). These facts proved that neopullulanase catalyzed all four types of reactions: hydrolysis of alpha-(1----4)-glucosidic linkage, hydrolysis of alpha-(1----6)-glucosidic linkage, transglycosylation to form alpha-(1----4)-glucosidic linkage, and transglycosylation to form alpha-(1----6)-glucosidic linkage. The four reactions are typically catalyzed by alpha-amylase, pullulanase, cyclomaltodextrin glucanotransferase, and 1,4-alpha-D-glucan branching enzyme, respectively. These four enzymes have some structural similarities to one other, but reactions catalyzed by the enzymes are considered to be distinctive: the four reactions are individually catalyzed by each of the enzymes. The experimental results obtained from the analysis of the reaction of the neopullulanase exhibited that the four reactions can be catalyzed in the same mechanism.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1991

The malZ gene of Escherichia coli, a member of the maltose regulon, encodes a maltodextrin glucosidase.

We have characterized a maltodextrin glucosidase, previously described as a maltose-inducible, cytoplasmic enzyme that cleaves p-nitrophenyl-alpha-maltoside in Escherichia coli. The gene encoding the enzyme activity, referred to as malZ, is located at 9.3 min on the chromosomal map. We cloned the gene in a high copy number vector and purified the enzyme. It is a monomer, with an apparent molecular weight of 65,000. The enzyme degrades maltodextrins, ranging from maltotriose to maltoheptaose, to shorter oligosaccharides, the final hydrolysis products being maltose and glucose. We measured the kinetic parameters, Km and Vmax, for the hydrolysis to glucose of the five different substrates. The binding of the substrate is enhanced by increasing the number of glucosyl residues in the maltodextrin. In contrast, the maximum rate of hydrolysis (Vmax) is fastest for maltotriose. To study the mode of action of the enzyme, we quantitatively measured the amount of free glucose liberated from the different maltodextrin substrates after a long incubation. More glucose is liberated from the long dextrins, as compared to the shorter ones, showing that the primary hydrolysis product was glucose, not maltose. Furthermore, [14C]maltotriose, specifically labeled at the reducing end, was hydrolyzed to [14C]glucose and unlabeled maltose. These data demonstrate that the malZ gene product is a maltodextrin glucosidase, liberating glucose from the reducing end of malto-oligosaccharides. The nucleotide sequence of malZ and the deduced amino acid sequence showed that malZ encodes a protein with a molecular weight of 68,960. Homology to glucosidases, alpha-amylases, and pullulanases were observed. Conserved regions thought to represent active sites in dextrin hydrolases were found in the MalZ protein.

Amino Acid Sequence↗