Three-dimensional structure of a variant `Termamyl-like' Geobacillus stearothermophilus α-amylase at 1.9 Å resolution.

The enzyme-catalysed degradation of starch is central to many industrial processes, including sugar manufacture and first-generation biofuels. Classical biotechnological platforms involve steam explosion of starch followed by the action of endo-acting glycoside hydrolases termed α-amylases and then exo-acting α-glucosidases (glucoamylases) to yield glucose, which is subsequently processed. A key enzymatic player in this pipeline is the `Termamyl' class of bacterial α-amylases and designed/evolved variants thereof.

Toward fast determination of protein stability maps: experimental and theoretical analysis of mutants of a Nocardiopsis prasina serine protease.

The stability of serine proteases is of major importance for their application in industrial processes. Here we study the determinants of the stability of a Nocardiopsis prasina serine protease using fast residual activity assays, a feature classification algorithm, and structure-based energy calculation algorithms for 121 micropurified mutant enzyme clones containing multiple point mutations. Using a multivariate regression analysis, we deconvolute the data for the mutant clones and find that mutations of residues Asn47 and Pro124 are deleterious to the stability of the enzyme.

Activity of three β-1,4-galactanases on small chromogenic substrates.

β-1,4-Galactanases belong to glycoside hydrolase family GH 53 and degrade galactan and arabinogalactan side chains of the complex pectin network in plant cell walls. Two fungal β-1,4-galactanases from Aspergillus aculeatus, Meripileus giganteus and one bacterial enzyme from Bacillus licheniformis have been kinetically characterized using the chromogenic substrate analog 4-nitrophenyl β-1,4-d-thiogalactobioside synthesized by the thioglycoligase approach. Values of k(cat)/K(m) for this substrate with A.

Structural and biochemical studies elucidate the mechanism of rhamnogalacturonan lyase from Aspergillus aculeatus.

We present here the first experimental evidence for bound substrate in the active site of a rhamnogalacturonan lyase belonging to family 4 of polysaccharide lyases, Aspergillus aculeatus rhamnogalacturonan lyase (RGL4). RGL4 is involved in the degradation of rhamnogalacturonan-I, an important pectic plant cell wall polysaccharide. Based on the previously determined wild-type structure, enzyme variants RGL4_H210A and RGL4_K150A have been produced and characterized both kinetically and structurally, showing that His210 and Lys150 are key active-site residues.

Understanding how diverse beta-mannanases recognize heterogeneous substrates.

The mechanism by which polysaccharide-hydrolyzing enzymes manifest specificity toward heterogeneous substrates, in which the sequence of sugars is variable, is unclear. An excellent example of such heterogeneity is provided by the plant structural polysaccharide glucomannan, which comprises a backbone of beta-1,4-linked glucose and mannose units. beta-Mannanases, located in glycoside hydrolase (GH) families 5 and 26, hydrolyze glucomannan by cleaving the glycosidic bond of mannosides at the -1 subsite.

Investigating the binding of beta-1,4-galactan to Bacillus licheniformis beta-1,4-galactanase by crystallography and computational modeling.

Microbial beta-1,4-galactanases are glycoside hydrolases belonging to family 53, which degrade galactan and arabinogalactan side chains in the hairy regions of pectin, a major plant cell wall component. They belong to the larger clan GH-A of glycoside hydrolases, which cover many different poly- and oligosaccharidase specificities. Crystallographic complexes of Bacillus licheniformis beta-1,4-galactanase and its inactive nucleophile mutant have been obtained with methyl-beta(1-->4)-galactotetraoside, providing, for the first time, information on substrate binding to the aglycone side of the beta-1,4-galactanase substrate binding groove.

Between-species variation in the kinetic stability of TIM proteins linked to solvation-barrier free energies.

Theoretical, computational, and experimental studies have suggested the existence of solvation barriers in protein unfolding and denaturation processes. These barriers are related to the finite size of water molecules and can be envisioned as arising from the asynchrony between water penetration and breakup of internal interactions. Solvation barriers have been proposed to play roles in protein cooperativity and kinetic stability; therefore, they may be expected to be subject to natural selection.

Beyond Lumry-Eyring: an unexpected pattern of operational reversibility/irreversibility in protein denaturation.

We have found that, contrary to naïve intuition, the degree of operational reversibility in the thermal denaturation of lipase from Thermomyces lanuginosa (an important industrial enzyme) in urea solutions is maximum when the protein is heated several degrees above the end of the temperature-induced denaturation transition. Upon cooling to room temperature, the protein seems to reach a state with enzymatic activity similar to that of the initial native state, but with higher denaturation temperature and radically different behavior in terms of susceptibility to irreversible denaturation. These results show that patterns of operational reversibility/irreversibility in protein denaturation may be more complex than the often-taken-for-granted, two-situation classification (reversible vs.

Characterization and three-dimensional structures of two distinct bacterial xyloglucanases from families GH5 and GH12.

The plant cell wall is a complex material in which the cellulose microfibrils are embedded within a mesh of other polysaccharides, some of which are loosely termed "hemicellulose." One such hemicellulose is xyloglucan, which displays a beta-1,4-linked d-glucose backbone substituted with xylose, galactose, and occasionally fucose moieties. Both xyloglucan and the enzymes responsible for its modification and degradation are finding increasing prominence, reflecting both the drive for enzymatic biomass conversion, their role in detergent applications, and the utility of modified xyloglucans for cellulose fiber modification.

Role of solvation barriers in protein kinetic stability.

The stability of several protein systems of interest has been shown to have a kinetic basis. Besides the obvious biotechnological implications, the general interest of understanding protein kinetic stability is emphasized by the fact that some emerging molecular approaches to the inhibition of amyloidogenesis focus on the increase of the kinetic stability of protein native states. Lipases are among the most important industrial enzymes.

Directed evolution of enzyme stability.

Modern enzyme development relies to an increasing extent on strategies based on diversity generation followed by screening for variants with optimised properties. In principle, these directed evolution strategies might be used for optimising any enzyme property, which can be screened for in an economically feasible way, even if the molecular basis of that property is not known. Stability is an interesting property of enzymes because (1) it is of great industrial importance, (2) it is relatively easy to screen for, and (3) the molecular basis of stability relates closely to contemporary issues in protein science such as the protein folding problem and protein folding diseases.

Structure of a Bacillus halmapalus family 13 alpha-amylase, BHA, in complex with an acarbose-derived nonasaccharide at 2.1 A resolution.

The enzymatic digestion of starch by alpha-amylases is one of the key biotechnological reactions of recent times. In the search for industrial biocatalysts, the family GH13 alpha-amylase BHA from Bacillus halmapalus has been cloned and expressed. The three-dimensional structure at 2.

Purification, crystallization and preliminary X-ray crystallographic studies on acetolactate decarboxylase.

Acetolactate decarboxylase has the unique ability to decarboxylate both enantiomers of acetolactate to give a single enantiomer of the decarboxylation product, (R)-acetoin. A gene coding for alpha-acetolactate decarboxylase from Bacillus brevis (ATCC 11031) was cloned and overexpressed in B. subtilis.

Structure of two fungal beta-1,4-galactanases: searching for the basis for temperature and pH optimum.

beta-1,4-Galactanases hydrolyze the galactan side chains that are part of the complex carbohydrate structure of the pectin. They are assigned to family 53 of the glycoside hydrolases and display significant variations in their pH and temperature optimum and stability. Two fungal beta-1,4-galactanases from Myceliophthora thermophila and Humicola insolens have been cloned and heterologously expressed, and the crystal structures of the gene products were determined.

Synthetic shuffling expands functional protein diversity by allowing amino acids to recombine independently.

We describe synthetic shuffling, an evolutionary protein engineering technology in which every amino acid from a set of parents is allowed to recombine independently of every other amino acid. With the use of degenerate oligonucleotides, synthetic shuffling provides a direct route from database sequence information to functional libraries. Physical starting genes are unnecessary, and additional design criteria such as optimal codon usage or known beneficial mutations can also be incorporated.

Industrial enzyme applications.

The effective catalytic properties of enzymes have already promoted their introduction into several industrial products and processes. Recent developments in biotechnology, particularly in areas such as protein engineering and directed evolution, have provided important tools for the efficient development of new enzymes. This has resulted in the development of enzymes with improved properties for established technical applications and in the production of new enzymes tailor-made for entirely new areas of application where enzymes have not previously been used.