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.

The structure of the small laccase from Streptomyces coelicolor reveals a link between laccases and nitrite reductases.

The X-ray structure of the two-domain laccase (small laccase) from Streptomyces coelicolor A3(2) was solved at 2.7-A resolution. The enzyme differs significantly from all laccases studied structurally so far.

Structural and mutational analyses of the interaction between the barley alpha-amylase/subtilisin inhibitor and the subtilisin savinase reveal a novel mode of inhibition.

Subtilisins represent a large class of microbial serine proteases. To date, there are three-dimensional structures of proteinaceous inhibitors from three families in complex with subtilisins in the Protein Data Bank. All interact with subtilisin via an exposed loop covering six interacting residues.

High-level expression of the native barley alpha-amylase/subtilisin inhibitor in Pichia pastoris.

An expression system for high-level expression of the native Hordeum vulgare alpha-amylase/subtilisin inhibitor (BASI) has been developed in Pichia pastoris, using the methanol inducible alcohol oxidase 1 (AOX1) promoter. To optimize expression, two codon-optimized coding regions have been designed and expressed alongside the wild-type coding region. To ensure secretion of the native mature protein, a truncated version of the alpha mating factor secretion signal from Saccharomyces cerevisiae was used.

Crystallization and preliminary X-ray diffraction analysis of the small laccase from Streptomyces coelicolor.

The small bacterial laccase from the actinobacterium Streptomyces coelicolor which lacks the second of the three domains of the laccases structurally characterized to date was crystallized. This multi-copper phenol oxidase crystallizes in a primitive tetragonal lattice, with unit-cell parameters a = b = 179.8, c = 175.

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.