Kinetic studies on the hydrolyses of alpha-, beta-, and gamma-cyclodextrins by Taka-amylase A

Marine enzymes: Classification and application in various industries

Oceans are regarded as a plentiful and sustainable source of biological compounds. Enzymes are a group of marine biomaterials that have recently drawn more attention because they are produced in harsh environmental conditions such as high salinity, extensive pH, a wide temperature range, and high pressure. Hence, marine-derived enzymes are capable of exhibiting remarkable properties due to their unique composition. In this review, we overviewed and discussed characteristics of marine enzymes as well as the sources of marine enzymes, ranging from primitive organisms to vertebrates, and presented the importance, advantages, and challenges of using marine enzymes with a summary of their applications in a variety of industries. Current biotechnological advancements need the study of novel marine enzymes that could be applied in a variety of ways. Resources of marine enzyme can benefit greatly for biotechnological applications duo to their biocompatible, ecofriendly and high effectiveness. It is beneficial to use the unique characteristics offered by marine enzymes to either develop new processes and products or improve existing ones. As a result, marine-derived enzymes have promising potential and are an excellent candidate for a variety of biotechnology applications and a future rise in the use of marine enzymes is to be anticipated.

Biochemical features and kinetic properties of α-amylases from marine organisms

Marine organisms have the ability of producing enzymes with unique properties compared to those of the same enzymes from terrestrial organisms. α-Amylases are among the most important extracellular enzymes found in various groups of organisms such as plants, animals and microorganisms. They play important roles in their carbohydrates metabolism of each organism. Microbial production of α-amylases is more effective than other sources of the enzyme. Many microorganisms are known to produce α-amylase including bacteria, yeasts, fungi and actinomycetes. However, enzymes from fungal and bacterial sources have dominated applications in industrial sectors. This review deals with what is known about the kinetics, biochemical properties and applications of these enzymes that have only been found in them and not in other α-amylases, and discussing their mechanistic and regulatory implications.

Enzymatic conversions of starch

This article surveys methods for the enzymatic conversion of starch, involving hydrolases and nonhydrolyzing enzymes, as well as the role of microorganisms producing such enzymes. The sources of the most common enzymes are listed. These starch conversions are also presented in relation to their applications in the food, pharmaceutical, pulp, textile, and other branches of industry. Some sections are devoted to the fermentation of starch to ethanol and other products, and to the production of cyclodextrins, along with the properties of these products. Light is also shed on the enzymes involved in the digestion of starch in human and animal organisms. Enzymatic processes acting on starch are useful in structural studies of the substrates and in understanding the characteristics of digesting enzymes. One section presents the application of enzymes to these problems. The information that is included covers the period from the early 19th century up to 2009.

Cyclomaltoheptaose mixed esters of anti-inflammatory drugs and short-chain fatty acids and study of their enzymatic hydrolysis in vitro

In an effort to enhance the drug-loading capacity of cyclomaltoheptaose (beta-cyclodextrin, betaCD) and to combine the function of anti-inflammatory drugs with short-chain fatty acids (SCFA), ternary esters incorporating seven copies of an anti-inflammatory drug and 14 copies of a SCFA onto a beta-cyclodextrin core were designed and prepared. Acetic, propionic, or butyric esters were introduced at secondary OH groups, and ibuprofen, flurbiprofen, or felbinac was attached to primary OH groups through ester bonds. Heptakis[2,3-di-O-butanoyl-6-O-2-(biphenyl-4-yl)-ethanoyl]-cyclomaltoheptaose was very stable in aqueous and esterase solution. It was hydrolyzed by alpha-amylase (4 units/mL) with t(1/2) value of 18h. The total released amount of biphenyl acetic acid was 38% after 24h when the esterase was added after the alpha-amylase hydrolysis. The present results suggest that these nine betaCD conjugates may release the anti-inflammatory drug in the colonic contents.

Degradation of raw or film-incorporated β-cyclodextrin by enzymes and colonic bacteria

beta-cyclodextrin (beta-CD) is a suitable excipient for peroral use, which improves the solubility of lipophilic drugs, as well as for colon-specific drug release when it is mixed with coating polymers. The first aim of this work was to examine the suitability of various enzymes as a simple in vitro model for the glycolytic activity in the human colon. alpha-Amylase (source Aspergillus oryzae) and taka diastase (source A. oryzae) showed remarkable degradation capacity of free beta-CD, whereas other alpha-amylases (sources Bacillus subtilis or Hog pancreas) were found to be unsuitable. The next aim was to find out if film-incorporated beta-CD is also degraded by these enzymes. Therefore, diffusion studies of 5-aminosalicylic acid (5-ASA) through Eudragit RS or Eudragit NE films containing beta-CD were performed with taka diastase present in the buffer medium. Pronounced diffusion of the drug through the Eudragit RS film was found only when swelling excipients like crosslinked sodium carboxymethylcellulose (CMC-CL sodium) or polyvinylpyrrolidone (PVP 25) were present in the film, indicating enhanced accessibility of beta-CD by the enzyme. Films containing CMC-CL without beta-CD showed even higher permeability, which also points to enzymatic degradation of CMC-CL. Permeabilization by taka diastase of Eudragit NE films without swelling agents correlated with the beta-CD content, whereas control films containing talcum remained impermeable upon enzyme action. Furthermore, the beta-CD degradation capacity of colonic bacteria like Escherichia fergusonii, Serratia odorifera or Proteus mirabilis was examined with beta-CD coatings on tablets, which contained bisoprolol as a model drug. Tablets with beta-CD-containing Eudragit RS coatings showed the highest drug release upon incubation with P. mirabilis. The moderate drug release by E. fergusonii could be increased almost to the same level when the bacteria were pre-incubated for 24 h in medium containing 2.5 mg/ml beta-CD, indicating the induction of glycolytic enzymes by beta-CD in this colonic bacteria strain.

Crystal structures and structural comparison of Thermoactinomyces vulgaris R-47 alpha-amylase 1 (TVAI) at 1.6 A resolution and alpha-amylase 2 (TVAII) at 2.3 A resolution

The X-ray crystal structures of Thermoactinomyces vulgaris R-47 alpha-amylase 1 (TVAI) and alpha-amylase 2 (TVAII) have been determined at 1.6 A and 2.3 A resolution, respectively. The structures of TVAI and TVAII have been refined, R-factor of 0.182 (R(free)=0.206) and 0.179 (0.224), respectively, with good chemical geometries. Both TVAI and TVAII have four domains, N, A, B and C, and all very similar in structure. However, there are some differences in the structures between them. Domain N of TVAI interacts strongly with domains A and B, giving a spherical shape structure to the enzyme, while domain N of TVAII is isolated from the other domains, which leads to the formation of a dimer. TVAI has three bound Ca ions, whereas TVAII has only one. TVAI has eight extra loops compared to TVAII, while TVAII has two extra loops compared to TVAI. TVAI can hydrolyze substrates more efficiently than TVAII with a high molecular mass such as starch, while TVAII is much more active against cyclodextrins than TVAI and other alpha-amylases. A structural comparison of the active sites has clearly revealed this difference in substrate specificity.

Plant alpha-amylase inhibitors and their interaction with insect alpha-amylases

Insect pests and pathogens (fungi, bacteria and viruses) are responsible for severe crop losses. Insects feed directly on the plant tissues, while the pathogens lead to damage or death of the plant. Plants have evolved a certain degree of resistance through the production of defence compounds, which may be aproteic, e.g. antibiotics, alkaloids, terpenes, cyanogenic glucosides or proteic, e.g. chitinases, beta-1,3-glucanases, lectins, arcelins, vicilins, systemins and enzyme inhibitors. The enzyme inhibitors impede digestion through their action on insect gut digestive alpha-amylases and proteinases, which play a key role in the digestion of plant starch and proteins. The natural defences of crop plants may be improved through the use of transgenic technology. Current research in the area focuses particularly on weevils as these are highly dependent on starch for their energy supply. Six different alpha-amylase inhibitor classes, lectin-like, knottin-like, cereal-type, Kunitz-like, gamma-purothionin-like and thaumatin-like could be used in pest control. These classes of inhibitors show remarkable structural variety leading to different modes of inhibition and different specificity profiles against diverse alpha-amylases. Specificity of inhibition is an important issue as the introduced inhibitor must not adversely affect the plant's own alpha-amylases, nor the nutritional value of the crop. Of particular interest are some bifunctional inhibitors with additional favourable properties, such as proteinase inhibitory activity or chitinase activity. The area has benefited from the recent determination of many structures of alpha-amylases, inhibitors and complexes. These structures highlight the remarkable variety in structural modes of alpha-amylase inhibition. The continuing discovery of new classes of alpha-amylase inhibitor ensures that exciting discoveries remain to be made. In this review, we summarize existing knowledge of insect alpha-amylases, plant alpha-amylase inhibitors and their interaction. Positive results recently obtained for transgenic plants and future prospects in the area are reviewed.

Role of Phe286 in the recognition mechanism of cyclomaltooligosaccharides (cyclodextrins) by Thermoactinomyces vulgaris R-47 alpha-amylase 2 (TVAII). X-ray structures of the mutant TVAIIs, F286A and F286Y, and kinetic analyses of the Phe286-replaced mutant TVAIIs

Phe286 located in the center of the active site of alpha-amylase 2 from Thermoactinomyces vulgaris R-47 (TVAII) plays an important role in the substrate recognition for cyclomaltooligosaccharides (cyclodextrins). The X-ray structures of mutant TVAIIs with the replacement of Phe286 by Ala (F286A) and Tyr (F286Y) were determined at 3.2 A resolution. Their structures have no significant differences from that of the wild-type enzyme. The kinetic analyses of Phe286-replaced variants showed that the variants with non-aromatic residues, Ala (F286A) and Leu (F286L), have lower enzymatic activities than those with aromatic residues, Tyr (F286Y) and Trp (F286W), and the replacement of Phe286 affects enzymatic activities for CDs more than those for starch.

Mechanism of porcine pancreatic alpha-amylase. Inhibition of amylose and maltopentaose hydrolysis by alpha-, beta- and gamma-cyclodextrins

The effects of alpha-, beta- and gamma-cyclodextrins on the amylose and maltopentaose hydrolysis catalysed by porcine pancreatic alpha-amylase (PPA) were investigated. The results of the statistical analysis performed on the kinetic data using the general initial velocity equation of a one-substrate reaction in the presence of one inhibitor indicate that the type of inhibition involved depends on the substrate used: the inhibition of amylose hydrolysis by alpha-, beta- and gamma-cyclodextrin is of the competitive type, while the inhibition of maltopentaose hydrolysis is of the mixed noncompetitive type. Consistently, the Lineweaver-Burk plots intersect on the vertical axis when amylose is used as the substrate, while in the case of maltopentaose, the intersection occurs at a point located in the second quadrant. The inhibition of the hydrolysis therefore involves only one abortive complex, PPA-cyclodextrin, when amylose is used as the substrate, while two abortive complexes, PPA-cyclodextrin and PPA-maltopentaose-cyclodextrin, are involved with maltopentaose. The mixed noncompetitive inhibition thus shows the existence of one accessory binding site. In any case, only one molecule of inhibitor binds to PPA. In line with these findings, the difference spectra of PPA produced by alpha-, beta- and gamma-cyclodextrin indicate that binding occurs at a tryptophan and a tyrosine residue. The corresponding dissociation constants and the inhibition constants obtained using the kinetic approach are in the same range (1.2-7 mM). The results obtained here on the inhibition of maltopentaose hydrolysis by cyclodextrin are similar to those previously obtained with acarbose as the inhibitor [Alkazaz, M., Desseaux, V., Marchis-Mouren, G., Prodanov, E. & Santimone, M. (1998) Eur. J. Biochem. 252, 100-107], but differ from those obtained with amylose as the substrate and acarbose as inhibitor [Alkazaz, M., Desseaux, V., Marchis-Mouren, G., Payan, F., Forest, E. & Santimone, M. (1996) Eur. J. Biochem. 241, 787-796]. It is concluded that the hydrolysis of both long and short chain substrates requires at least one secondary binding site, including a tryptophan residue.

Release characteristics of a short-chain fatty acid, n-butyric acid, from its beta-cyclodextrin ester conjugate in rat biological media

6(A)-O-(n-Butanoyl)-beta-cyclodextrin was prepared and its hydrolysis behavior in aqueous solutions and in rat intestinal fluids was investigated. Furthermore, the enzymatic hydrolyses of the n-butyric acid-beta-cyclodextrin conjugate using alpha-amylase and esterase were studied to gain insight into the release behavior of n-butyric acid from the conjugate. The hydrolysis of the conjugate proceeded according to a first-order kinetics in aqueous solution, and gave a V-shaped pH profile, indicating a specific acid-base-catalyzed hydrolysis at acidic and neutral-alkaline regions, respectively. The half-lives (t(1/2)) of the conjugate at pH 4.4, 6.8, and 7.4 at 37 degrees C were approximately 580, 43, and 6 days, respectively, indicating that the conjugate is stable in aqueous solution. No appreciable release of n-butyric acid from the conjugate was observed in the stomach and small intestinal contents of rats, or in the small and large intestinal homogenates of rats. On the other hand, a fast disappearance of the conjugate and an appearance of n-butyric acid were observed in the cecal and colonic contents of rats. The t(1/2) values of the disappearance were approximately 4, 1, and 6 h in 10 and 15% cecal contents and 10% colonic contents, respectively, and the appearance of n-butyric acid after 6 h was approximately 10% in the 15% cecal contents. Aspergillus oryzae alpha-amylase hydrolyzed the conjugate to small saccharide conjugates, such as the triose and maltose conjugates, but there was no appreciable release of n-butyric acid. The conjugate was less susceptible to carboxylic esterase (from porcine live), thus releasing no appreciable amounts of n-butyric acid. On the other hand, a fast release of n-butyric acid was observed when the esterase was employed after amylase hydrolysis, suggesting that two types of enzymes, sugar-degrading and ester-hydrolyzing enzymes, are necessary for the release of n-butyric acid from the conjugate in large intestinal contents.

Kinetics and inhibition of cyclomaltodextrinase from alkalophilic Bacillus sp. I-5

The cyclomaltodextrinase from alkalophilic Bacillus sp. I-5 (CDase I-5) was expressed in Escherichia coli and the purified enzyme was used for characterization of the enzyme action. The hydrolysis products were monitored by both HPLC and high-performance ion chromatography analysis that enable the kinetic analysis of the cyclomaltodextrin (CD)-degrading reaction. Analysis of the kinetics of cyclomaltodextrin hydrolysis by CDase I-5 indicated that ring-opening of the cyclomaltodextrin was the major limiting step and that CDase I-5 preferentially degraded the linear maltodextrin chain by removing the maltose unit. The substrate binding affinity of the enzyme was almost same for those of cyclomaltodextrins while the rate of ring-opening was the fastest for cyclomaltoheptaose. Acarbose and methyl 6-amino-6-deoxy-alpha-d-glucopyranoside were relatively strong competitive inhibitors with K(i) values of 1.24 x 10(-3) and 8.44 x 10(-1) mM, respectively. Both inhibitors are likely to inhibit the ring-opening step of the CD degradation reaction.

Crystal structure of Thermoactinomyces vulgaris R-47 alpha-amylase II (TVAII) hydrolyzing cyclodextrins and pullulan at 2.6 A resolution

The crystal structure of Thermoactinomyces vulgaris R-47 alpha-Amylase II (TVAII) has been determined by multiple isomorphous replacement at 2.6 A resolution. TVAII was crystallized in an orthorhombic system with the space group P212121 and the cell dimensions a=118.5 A, b=119.5 A, c=114.5 A. There are two molecules in an asymmetric unit, related by the non-crystallographic 2-fold symmetry. Diffraction data were collected at 113 K and the cell dimensions reduced to a=114.6 A, b=117.9 A, c=114.2 A, and the model was refined against 7.0-2.6 A resolution data giving an R-factor of 0.204 (Rfree=0.272). The final model consists of 1170 amino acid residues (two molecules) and 478 water molecules with good chemical geometry. TVAII has three domains, A, B, and C, like other alpha-amylases. Domain A with a (beta/alpha)8 barrel structure and domain C with a beta-sandwich structure are very similar to those found in other alpha-amylases. Additionally, TVAII has an extra domain N composed of 121 amino acid residues at the N-terminal site, which has a beta-barrel-like structure consisting of seven antiparallel beta-strands. Domain N is one of the driving forces in the formation of the dimer structure of TVAII, but its role in the enzyme activity is still not clear. TVAII does not have the Ca2+ binding site that connects domains A and B in other alpha-amylases, rather the NZ atom of Lys299 of TVAII serves as the connector between these domains. TVAII can hydrolyze cyclodextrins and pullulan as well as starch. Based on a structural comparison with the complex between a mutant cyclodextrin glucanotransferase and a beta-cyclodextrin derivative, Phe286 located at domain B is considered the residue most likely to recognize the hydrophobic cavity of cyclodextrins. The active-site cleft of TVAII is wider and shallower than that of other alpha-amylases, and seems to be suitable for the binding of pullulan which is expected not to adopt the helical structure of amylose.

6A-O-[(4-biphenylyl)acetyl]-alpha-, -beta-, and -gamma-cyclodextrins and 6A-deoxy-6A-[[(4-biphenylyl)acetyl]amino]-alpha-, -beta-, and -gamma-cyclodextrins: potential prodrugs for colon-specific delivery

Cyclodextrins (CyDs) are known to be fermented to small saccharides by colonic microflora, whereas they are only slightly hydrolyzable and thus are not easily absorbed in the stomach and small intestine. This property of CyDs is particularly useful for colon-specific delivery of drugs. In this study, an antiinflammatory 4-biphenylylacetic acid (BPAA) was selectively conjugated onto one of the primary hydroxyl groups of alpha-, beta-, and gamma-CyDs through an ester or amide linkage, 6A-O-[(4-biphenylyl)acetyl[-alpha-, -beta-, and -gamma-CyDs (1-3) and 6A-deoxy-6A-[[(4-biphenylyl)acetyl]amino]-alpha-, -beta-, and -gamma-CyDs (4-6). In rat cecal and colonic contents (10%, w/v), 1 and 3 released more than 95% of BPAA within 1-2 h, and 2 released about 50% of the drug within 12 h. The amide prodrugs, 4-6, did not release BPAA in the cecal contents, but gave BPAA/maltose or BPAA/triose conjugates linked through an amide bond. On the other hand, these prodrugs were found to be stable in the contents of rat stomachs and small intestines, in intestinal or liver homogenates, and in rat blood. The serum levels of BPAA increased about 3 h after oral administration of 1 and 3 to rats, accompanying a marked increase in the serum levels, whereas 2 and 4-6 resulted in little increase of the serum levels. These facts suggest that BPAA is released after the ring opening of CyDs followed by the ester hydrolysis, and the BPAA activation takes place site-specifically in the cecum and colon. Therefore, the present CyD prodrug approach provides a versatile means of constructing a novel colon-specific drug delivery system.

Metabolism of cyclodextrins by Klebsiella oxytoca m5a1: purification and characterisation of a cytoplasmically located cyclodextrinase

It has been shown previously that the products of 11 genes are required for metabolism of starch by Klebsiella oxytoca via a novel pathway. An extracellular cyclodextrin glucanotransferase first degrades starch into alpha- and beta-cyclodextrins; evidence then has been presented that the cyclodextrins are transported into the cytoplasma via a specific system and that they are metabolised inside the cell. To provide support for this model, we have analysed whether Klebsiella oxytoca possesses a cytoplasmic enzyme able to linearise cyclodextrins. A possible candidate was the product of the cymH gene since it displays sequence similarity with cyclodextrinases from other organisms. The cymH gene was overexpressed, and the CymH protein was purified. CymH is a monomer of 69 kDa molecular mass and hydrolysed cyclodextrins at an optimum pH of 7.0 and an optimum temperature of 23 degrees C, respectively. The apparent Km increased with increasing size of the cyclodextrins, but the reaction velocity decreased. Linear malto-oligosaccharides were also accepted as substrates, but were hydrolysed with a lower efficiency. Final products in each case were maltose and maltotriose. It was demonstrated by immunoblotting that CymH is located in the cytoplasm and that no signal peptide was cleaved off. Since cymH mutants were no longer able to grow on cyclodextrins, these results prove that cyclodextrins are degraded inside the cell, and they support the contention of the existence of a specific transport system.

Purification and characterization of periplasmic alpha-amylase from Xanthomonas campestris K-11151

Xanthomonas campestris K-11151, isolated from soil, produced a periplasmic alpha-amylase of a new type. The enzyme was purified to homogeneity, as shown by several criteria. The purified enzyme showed almost the same activities on alpha-, beta-, and gamma-cyclodextrins, soluble starch, and amylose. Moreover, it was active on branched cyclodextrins, pullulan, and maltose but not on glycogen. Kinetic analysis showed that alpha-cyclodextrin was the best substrate among the cyclodextrins. The substrate specificity suggested that this enzyme had the combined activities of alpha-amylase, cyclodextrinase, and neopullulanase.

Models for the action of barley alpha-amylase isozymes on linear substrates

The formation of maltodextrins, G1 to G12, during the hydrolysis of amylose by alpha-amylases 1 and 2 from barley malt was followed by HPLC. Similar, but not identical, distributions of products were obtained with the two alpha-amylase components. Maltose, G6, and G7 were major products, but G7 was degraded as hydrolysis proceeded. alpha-Amylase 1 produced more G1 and G3 than did alpha-amylase 2 at all stages of hydrolysis. Products formed during the hydrolysis of G9, G10, G11, and G12 by the two alpha-amylases were also determined. A different spectrum of products was observed with each substrate and small differences were observed in the action pattern of the two alpha-amylases, e.g., G3 and G7 were the major products formed during the hydrolysis of G10 by alpha-amylase 1, whereas G2 and G8 were the major products formed by alpha-amylase 2 on the same substrate. These results were used to develop a model of the active site of barley malt alpha-amylases. This site contains ten contiguous subsites with the catalytic site situated between subsites 7 and 8. The model can be used to predict hydrolysis patterns of amylose and maltodextrins by cereal alpha-amylases.

Structure of the gene encoding cyclomaltodextrinase from Clostridium thermohydrosulfuricum 39E and characterization of the enzyme purified from Escherichia coli

Clostridium thermohydrosulfuricum 39E, a gram-positive thermophilic anaerobic bacterium, produced a cyclodextrin (CD)-degrading enzyme, cyclodextrinase (CDase) (EC 3.2.1.54). The enzyme was purified to homogeneity from Escherichia coli cells carrying a recombinant multicopy plasmid that contained the gene encoding for thermophilic CDase. The purified enzyme was a monomer with an M(r) of 66,000 +/- 2,000. It showed the highest activity at pH 5.9 and 65 degrees C. The enzyme hydrolyzed alpha-, beta-, and gamma-CD and linear maltooligosaccharides to yield maltose and glucose. The Km values for alpha-, beta-, and gamma-CD were 2.5, 2.1, and 1.3 mM, respectively. The rates of hydrolysis for polysaccharides (starch, amylose, amylopectin, and pullulan) were less than 5% of the rate of hydrolysis for alpha-CD. The entire nucleotide sequence of the CDase gene was determined. The deduced amino acid sequence of CDase, consisting of 574 amino acids, showed some similarities with those of various amylolytic enzymes.

Purification and some properties of cyclodextrin-hydrolyzing enzyme from Bacillus sphaericus

An intracellular cyclodextrin-hydrolyzing enzyme from Bacillus sphaericus E-244 isolated from soil was purified to a homogeneous state by means of Triton X-100 extraction, DEAE-Sepharose column chromatography, hydrophobic and molecular-sieve HPLC. The enzyme was estimated to have an Mr of 72,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis and 144,000 by HPLC gel filtration on TSK gel G 3000 SW. It had a pH optimum of 8.0, and the enzyme, stable at 25 degrees C and pH 5.5-9.5 for 24 h, was inactivated at 50 degrees C for 10 min. The enzyme hydrolyzed beta-cyclodextrin more effectively than linear maltooligosaccharides such as maltopentaose, maltohexaose and maltoheptaose or polysaccharides such as starch, amylopectin, amylose and pullulan.

In vitro action of human and porcine alpha-amylases on cyclomalto-oligosaccharides

The vitro action of human and porcine pancreatic alpha-amylases on cyclomalto-oligosaccharides (cyclodextrins) was investigated both by a high-performance liquid chromatographic analysis and a quantitative analysis of the reducing power of cyclodextrin hydrolyzates. Cyclomalto-octaose (gamma-cyclodextrin) was hydrolyzed to produce mainly maltose, but cyclomalto-hexaose and -heptaose were little affected both by human and porcine alpha-amylases. Quantitative analysis of reducing power revealed that the ring-opening rate of gamma-cyclodextrin catalyzed by human pancreatic alpha-amylase was 2.8 times slower than that catalyzed by the porcine enzyme. The number of multiple attacks on gamma-cyclodextrin and its inhibitor constants for human pancreatic alpha-amylase and porcine pancreatic alpha-amylase were almost the same.

Characterization of thermostable cyclodextrinase from Clostridium thermohydrosulfuricum 39E

Clostridium thermohydrosulfuricum 39E produced a cell-bound cyclodextrin (CD)-degrading enzyme (cyclodextrinase). It was partially purified 205-fold (specific activity, 14.5 U/mg of protein) by solubilizing with Triton X-100, ammonium sulfate treatment, and DEAE-Sepharose CL-6B column chromatography. The enzyme activity was found to be stable at pH 5.5 and 60 degrees C and optimally active at pH 6.0 and 65 degrees C. The enzyme preparation hydrolyzed CDs, with alpha-CD greater than beta-CD greater than gamma-CD, and displayed a putative multiple attack pattern. The enzyme activity was inhibited by p-chloromercuribenzoate but not by N-bromosuccinimide.

A super-secondary structure predicted to be common to several alpha-1,4-D-glucan-cleaving enzymes

Predictions of protein secondary structure are used with amino acid sequence alignments to show that the N-terminal domains of cyclodextrin glucanotransferases and a yeast alpha-glucosidase may have the same super-secondary structure as alpha-amylases, i.e. an (alpha/beta)8-barrel fold. Sequence similarities provide evidence that glucanotransferases, and possibly the glucosidase, are, like alpha-amylases, Ca2+-containing enzymes. The relationship between substrate specificity and the nature of the amino acid residues proposed at the active site is discussed for the transferases and alpha-glucosidase. A set of three programs for an Apple IIe computer to carry out the calculations described by Garnier, Osguthorpe & Robson [(1978) J. Mol. Biol. 120, 97-120] and a set of four programs for an Apple IIe computer to carry out the calculations described by Levin, Robson & Garnier [(1986) FEBS Lett. 205, 303-308] have been deposited as Supplementary Publication SUP 50149 (25 pages) at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1989) 257, 5.

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.

Purification and characterization of extracellular alpha-amylase and glucoamylase from the yeast Candida antarctica CBS 6678

An alpha-amylase and a glucoamylase were purified to homogeneity from the culture fluid of beta-cyclodextrin-grown Candida antarctica CBS 6678 by protamine sulfate treatment, ammonium sulfate precipitation, gel filtration (Sephadex G-75 sf, Ultrogel AcA 54), DEAE-Sephacel chromatography, hydroxyapatite chromatography and affinity chromatography on acarbose--AH-Sepharose 4B. Both enzymes were monomeric glycoproteins with fairly different amino acid compositions. Their apparent relative molecular mass, sedimentation coefficient (Szero20,w), isoelectric point, absorption coefficient (280 nm), pH and temperature optima were estimated as 48,500, 4.7 S, 10.1, 1.74 cm2 mg-1, 4.2 and 57 degrees C, respectively, for glucoamylase and as 50,000, 4.9 S, 10.3, 1.53 cm2 mg-1, 4.2 and 62 degrees C, respectively, for alpha-amylase. Kinetic analyses indicated that both enzymes preferentially hydrolyzed high-molecular-mass substrates, including some raw starches. alpha-Amylase was active on cyclodextrins, whereas debranching activity was demonstrated for glucoamylase. Trestatins were potent inhibitors of both alpha-amylase (Ki less than 1 microM) and glucoamylase (Ki less than 0.1 microM), being more effective than Bay e 4609 (Ki less than 10 microM). Glucoamylase was selectivity and strongly inhibited by acarbose (Ki less than 0.1 microM). Activity of the latter enzyme was also affected by 1-deoxynojirimycin (Ki less than 1 mM), maltitol and amino alcohols (Ki less than 10 mM). Unlike alpha-amylase, glucoamylase adsorbed strongly onto raw starch, the adsorption site being non-identical with the active site.

Purification and Characterization of Extracellular Amylolytic Enzymes from the Yeast Filobasidium capsuligenum

The extracellular amylolytic system of Filobasidium capsuligenum consisted of an α-amylase (1,4-α- d -glucan glucanhydrolase, EC 3.2.1.1) and two forms of glucoamylase (1,4-α- d -glucan glucohydrolase, EC 3.2.1.3). The enzymes were purified by ammonium sulfate fractionation, repeated ion-exchange chromatography (DEAE-Sephadex A-50), and gel filtration (Sephadex G-25, Sephadex G-100 sf). α-Amylase had an optimum pH of 5.6 and an optimum temperature of 50�C but was rapidly inactivated at higher temperature. The molecular weight was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 64,000. An acarbose concentration of 20 μg/ml was required for 50% inhibition of the α-amylase. Both glucoamylases are glycoproteins of identical molecular weight (60,000) and produce only glucose by exohydrolysis. The debranching activity of the glucoamylases was evidenced with substrates containing α-1,6 linkages. The pH optima were 5.0 to 5.6 for glucoamylase I and 4.8 to 5.3 for glucoamylase II. Glucoamylase I had a higher optimum temperature (55�C) than glucoamylase II (50�C) and was also more resistant to thermal inactivation. Only low acarbose concentrations (<0.1 μg/ml) were required to reduce the activity of the glucoamylases by 50%.