N-terminal amino acid sequence of Bacillus licheniformis alpha-amylase: comparison with Bacillus amyloliquefaciens and Bacillus subtilis Enzymes

Formation of Polyphenol-Denatured Protein Flocs in Alcohol Beverages Sweetened with Refined Cane Sugars

The sporadic appearance of floc from refined, white cane sugars in alcohol beverages remains a technical problem for both beverage manufacturers and sugar refiners. Cane invert sugars mixed with 60% pure alcohol and water increased light scattering by up to ∼1000-fold. Insoluble and soluble starch, fat, inorganic ash, oligosaccharides, Brix, and pH were not involved in the prevailing floc-formation mechanism. Strong polynomial correlations existed between the haze floc and indicator values (IVs) (color at 420 nm pH 9.0/color at pH 4.0-an indirect measure of polyphenolic and flavonoid colorants) (R² = 0.815) and protein (R² = 0.819) content of the invert sugars. Ethanol-induced denaturation of the protein exposed hydrophobic polyphenol-binding sites that were further exposed when heated to 80 °C. A tentative mechanism for floc formation was advanced by molecular probing with a haze (floc) active protein and polyphenol as well as polar, nonpolar, and ionic solvents.

Escherichia coli signal peptidase recognizes and cleaves the signal sequence of α-amylase originating from Bacillus licheniformis

The gene encoding the α-amylase from Bacillus licheniformis was cloned, with and without the native signal sequence, and expressed in Escherichia coli, resulting in the production of the recombinant protein in the cytoplasm as insoluble but enzymatically active aggregates. Expression with a low concentration of the inducer at low temperature resulted in the production of the recombinant protein in soluble form in a significantly higher amount. The protein produced with signal sequence was exported to the extracellular medium, whereas there was no export of the protein produced from the gene without the signal sequence. Similarly, the α-amylase activity in the culture medium increased with time after induction in case of the protein produced with signal sequence. Molecular mass determinations by MALDI-TOF mass spectrometry and N-terminal amino acid sequencing of the purified recombinant α-amylase from the extracellular medium revealed that the native signal peptide was cleaved by E. coli signal peptidase between Ala28 and Ala29. It seems possible that the signal peptide of α-amylase from B. licheniformis can be used for the secretion of other recombinant proteins produced using the E. coli expression system.

Purification and characterization of novel α-amylase from Bacillus subtilis KIBGE HAS

Purification of extracellular α-amylase from Bacillus subtilis KIBGE HAS was carried out by ultrafiltration, ammonium sulfate precipitation and gel filtration chromatography. The enzyme was purified to homogeneity with 96.3-fold purification with specific activity of 13011 U/mg. The molecular weight of purified α-amylase was found to be 56,000 Da by SDS-PAGE. Characteristics of extracellular α-amylase showed that the enzyme had a Km and V (max) value of 2.68 mg/ml and 1773 U/ml, respectively. The optimum activity was observed at pH 7.5 in 0.1 M phosphate buffer at 50 °C. The amino acid composition of the enzyme showed that the enzyme is rich in neutral/non polar amino acids and less in acidic/polar and basic amino acids. The N-terminal protein sequence of 10 residues was found to be as Ser-Ser-Asn-Lys-Leu-Thr-Thr-Ser-Trp-Gly (S-S-N-K-L-T-T-S-W-G). Furthermore, the protein was not N-terminally blocked. The sequence of α-amylase from B. subtilis KIBGE HAS was a novel sequence and showed no homology to other reported α-amylases from Bacillus strain.

Purification and characterization of the extracellular alpha-amylase from Clostridium acetobutylicum ATCC 824

The extracellular alpha-amylase (1,4-alpha-D-glucanglucanohydrolase; EC 3.2.1.1) from Clostridium acetobutylicum ATCC 824 was purified to homogeneity by anion-exchange chromatography (mono Q) and gel filtration (Superose 12). The enzyme had an isoelectric point of 4.7 and a molecular weight of 84,000, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was a monomeric protein, the 19-amino-acid N terminus of which displayed 42% homology with the Bacillus subtilis saccharifying alpha-amylase. The amino acid composition of the enzyme showed a high number of acidic and hydrophobic residues and only one cysteine residue per mole. The activity of the alpha-amylase was not stimulated by calcium ions (or other metal ions) or inhibited by EDTA, although the enzyme contained seven calcium atoms per molecule. alpha-Amylase activity on soluble starch was optimal at pH 5.6 and 45 degrees C. The alpha-amylase was stable at an acidic pH but very sensitive to thermal inactivation. It hydrolyzed soluble starch, with a Km of 3.6 g . liter-1 and a Kcat of 122 mol of reducing sugars . s-1 . mol-1. The alpha-amylase showed greater activity with high-molecular-weight substrates than with low-molecular-weight maltooligosaccharides, hydrolyzed glycogen and pullulan slowly, but did not hydrolyze dextran or cyclodextrins. The major end products of maltohexaose degradation were glucose, maltose, and maltotriose; maltotetraose and maltopentaose were formed as intermediate products. Twenty seven percent of the glucoamylase activity generally detected in the culture supernatant of C. acetobutylicum can be attributed to the alpha-amylase.

Microbial amylolytic enzymes

Starch-degrading, amylolytic enzymes are widely distributed among microbes. Several activities are required to hydrolyze starch to its glucose units. These enzymes include alpha-amylase, beta-amylase, glucoamylase, alpha-glucosidase, pullulan-degrading enzymes, exoacting enzymes yielding alpha-type endproducts, and cyclodextrin glycosyltransferase. Properties of these enzymes vary and are somewhat linked to the environmental circumstances of the producing organisms. Features of the enzymes, their action patterns, physicochemical properties, occurrence, genetics, and results obtained from cloning of the genes are described. Among all the amylolytic enzymes, the genetics of alpha-amylase in Bacillus subtilis are best known. Alpha-Amylase production in B. subtilis is regulated by several genetic elements, many of which have synergistic effects. Genes encoding enzymes from all the amylolytic enzyme groups dealt with here have been cloned, and the sequences have been found to contain some highly conserved regions thought to be essential for their action and/or structure. Glucoamylase appears usually in several forms, which seem to be the results of a variety of mechanisms, including heterogeneous glycosylation, limited proteolysis, multiple modes of mRNA splicing, and the presence of several structural genes.

Molecular cloning of an amylase gene of Bacillus circulans

An amylase gene of Bacillus circulans was cloned in B. subtilis and its nucleotide sequence was determined. The putative proamylase consists of 528 amino acids, which correspond to a molecular weight of 58,776. Homologous regions with other amylases of Bacillus species were found. A sigma 55-type promoter is located at about 250 bp upstream from the starting codon. This promoter was also functional in Escherichia coli, and able to express beta-galactosidase activity.

Structural genes encoding the thermophilic alpha-amylases of Bacillus stearothermophilus and Bacillus licheniformis

The genes encoding the thermostable alpha-amylases of Bacillus stearothermophilus and B. licheniformis were cloned in Escherichia coli, and their DNA sequences were determined. The coding and deduced polypeptide sequences are 59 and 62% homologous to each other, respectively. The B. stearothermophilus protein differs most significantly from that of B. licheniformis in that it possesses a 32-residue COOH-terminal tail. Transformation of E. coli with vectors containing either gene resulted in the synthesis and secretion of active enzymes similar to those produced by the parental organisms. A plasmid was constructed in which the promoter and the NH2-terminal two-thirds of the B. stearothermophilus coding sequence was fused out of frame to the entire mature coding sequence of the B. licheniformis gene. Approximately 1 in 5,000 colonies transformed with this plasmid was found to secrete an active amylase. Hybridization analysis of plasmids isolated from these amylase-positive colonies indicated that the parental coding sequences had recombined by homologous recombination. DNA sequence analysis of selected hybrid genes revealed symmetrical, nonrandom distribution of loci at which the crossovers had resolved. Several purified hybrid alpha-amylases were characterized and found to differ with respect to thermostability and specific activity.

Isolation and the 5'-end nucleotide sequence of Bacillus licheniformis alpha-amylase gene

We have isolated and determined the 5'-end nucleotide sequence of the alpha-amylase gene from Bacillus licheniformis ATCC 14580. The alpha-amylase produced by this strain is thermostable and of liquefying type. The gene was originally cloned in a bacteriophage lambda 1059 vector. A subclone containing a 5.3 X 10(3)-base insert in pBR322 was further characterized. The nucleotide sequence coding for the 5' end of the structural gene together with the sequence coding for the upstream control regions was determined. The deduced N-terminal amino acid sequence was identical with the previously published amino acid sequence of B. licheniformis alpha-amylase. There was also very strong homology to the N-terminal sequence of Bacillus amyloliquefaciens alpha-amylase. The Mr of the thermostable alpha-amylase, as determined in vitro in a cell-free transcription/translation system of Escherichia coli, was about 55 000.

Nucleotide sequence of the 5' region of the Bacillus licheniformis alpha-amylase gene: comparison with the B. amyloliquefaciens gene

The DNA sequence of the 5' region of the Bacillus licheniformis alpha-amylase gene is reported. Comparison of the inferred amino acid sequence of the B. licheniformis alpha-amylase gene with that of the Bacillus amyloliquefaciens gene shows that whereas the amino acid sequences of the mature proteins have considerable homology, the sequences for the signal peptides are distinct.

Molecular cloning in Bacillus subtilis of a Bacillus licheniformis gene encoding a thermostable alpha amylase

A resident-plasmid cloning system developed for Bacillus subtilis has been used to isolate recombinant plasmids carrying DNA from Bacillus licheniformis which confer alpha-amylase activity on alpha-amylase-negative mutants of B. subtilis. These plasmids contain a 3550-bp insert at the EcoRI site of the plasmid pBD64. Subcloning various lengths of the B. licheniformis DNA has localised the gene to a 2550-bp BclI fragment. We present evidence that the cloned fragment codes for a B. licheniformis heat-stable alpha-amylase with a temperature optimum of 93 degrees C. The foreign gene is expressed efficiently in B. subtilis and is stably maintained.

Glyceride-cysteine lipoproteins and secretion by Gram-positive bacteria

The membrane penicillinases of Bacillus licheniformis and Bacillus cereus are lipoproteins with N-terminal glyceride thioether modification identical to that of the Escherichia coli outer membrane lipoprotein. They are readily labeled with [3H]palmitate present during exponential growth. At the same time, a few other proteins in each organism become labeled and can be detected by fluorography after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total membrane proteins. We distinguish these proteins from the O-acyl proteolipids by demonstrating the formation of glyceryl cysteine sulfone after performic acid oxidation and hydrolysis of the protein. By this criterion, B. licheniformis and B. cereus contain sets of lipoproteins larger in average molecular weight than that of E. coli. Members of the sets probably are under a variety of physiological controls, as indicated by widely differing relative labeling intensity in different media. The set in B. licheniformis shares with membrane penicillinase a sensitivity to release from protoplasts by mild trypsin treatment, which suggests similar orientation on the outside of the membrane. At least one protein is the membrane-bound partner of an extracellular hydrophilic protein, the pair being related as membrane and exopenicillinases are. We propose that the lipoproteins of gram-positive organisms are the functional equivalent of periplasmic proteins in E. coli and other gram-negative bacteria, prevented from release by anchorage to the membrane rather than by a selectively impermeable outer membrane.