[The effect of point amino acid substitutions in an internal alpha-helix on thermostability of Aspergillus awamori X100 glucoamylase].

Conformational flexibility of alpha-helices in glucoamylase of the fungus Aspergillus awamori was studied by molecular dynamics methods. Several amino acid substitutions (G127A, P128A, I136L, G137A, and G139A) optimizing intrinsic interactions in one of the alpha-helices (D) within the hydrophobic core of this protein were constructed and studied. It was found that these point mutations had different effects on the glucoamylase thermal inactivation constant.

H-bonding in protein hydration revisited.

H-bonding between protein surface polar/charged groups and water is one of the key factors of protein hydration. Here, we introduce an Accessible Surface Area (ASA) model for computationally efficient estimation of a free energy of water-protein H-bonding at any given protein conformation. The free energy of water-protein H-bonds is estimated using empirical formulas describing probabilities of hydrogen bond formation that were derived from molecular dynamics simulations of water molecules at the surface of a small protein, Crambin, from the Abyssinian cabbage (Crambe abyssinica) seed.

Expression, isolation, purification, and biochemical properties of trehalose-6-phosphate hydrolase from thermoresistant strain Bacillus sp. GP16.

Here we describe cloning, expression, and purification of the enzyme trehalose-6-phosphate hydrolase from thermoresistant strain Bacillus sp. GP16. Principal biochemical properties of the enzyme at different pH and temperature values were determined.

alpha-Glucosidases.

This review highlights the main properties of mammalian, plant, and microbial alpha-glucosidases. Special attention is given to the classification of these enzymes, possible catalytic mechanisms, their tertiary structure, and the structure of major inhibitors. Experimental data on the elucidation of amino acid residues essential for catalysis are also discussed.

Crystallographic complexes of glucoamylase with maltooligosaccharide analogs: relationship of stereochemical distortions at the nonreducing end to the catalytic mechanism.

Crystal structures at pH 4 of complexes of glucoamylase from Aspergillus awamori var. X100 with the pseudotetrasaccharides D-gluco-dihydroacarbose and acarbose have been refined to R-factors of 0.147 and 0.

Refined structure for the complex of D-gluco-dihydroacarbose with glucoamylase from Aspergillus awamori var. X100 to 2.2 A resolution: dual conformations for extended inhibitors bound to the active site of glucoamylase.

The crystal structure at pH 4 of the complex of glucoamylase II(471) from Aspergillus awamori var. X100 with the pseudotetrasaccharide D-gluco-dihydroacarbose has been refined to an R-factor of 0.125 against data to 2.

NMR spectroscopy of exchangeable protons of glucoamylase and of complexes with inhibitors in the 9-15-ppm range.

1H-NMR spectra have been recorded for glucoamylases I and II from Aspergillus awamori var. X100 and from A. niger in the 9-15-ppm region.

Refined structure for the complex of acarbose with glucoamylase from Aspergillus awamori var. X100 to 2.4-A resolution.

The three-dimensional structure of the pseudotetrasaccharide acarbose complexed with glucoamylase II(471) from Aspergillus awamori var. X100 has been determined to 2.4-A resolution.

Refined crystal structures of glucoamylase from Aspergillus awamori var. X100.

The refined crystal structures of a proteolytic fragment of glucoamylase from Aspergillus awamori var. X100 have been determined at pH 6 and 4 to a resolution of 2.2 A and 2.

[Cleavage of O-glycosyl bonds in glycopeptides].

The possibility of cleavage of the alpha-bond between mannose (or galactose) and serine (or threonine) in the presence of alpha-mannosidase and alpha-galactosidase has been studied. Using model compounds simulating the O-glycosyl bond in glycoproteins, several glycopeptides have been synthesized: N-tertbutyloxycarbonyl-O-alpha-mannopyranosyl-seryl-glycine methylamide (alpha-Man-Ser-Gly), tertbutyl-oxycarbonyl-O-alpha-mannopyranosyl-threonyl- glycine methylamide (alpha-Man-Thr-Gly), N-tertbutyloxy-carbonyl-O-alpha-galactopyranosyl-seryl-glycine methylamide (alpha-Gal-Ser-Gly) as well as N-tertbutyloxy-carbonyl-O-beta-mannopyranosyl-seryl-glycine methylamide (beta-Man-Ser-Gly). The cleavage has been shown to occur in glucoamylase after proteolytic degradation.

A model for cleavage of O-glycosidic bonds in glycoproteins.

The present work investigated the possibility of cleavage of alpha-linkages between mannose or galactose and serine/threonine residues by alpha-mannosidase and alpha-galactosidase. The study was carried out initially with model synthetic compounds imitating the O-glycosidic bond in glycoproteins, and further with glucoamylase. It was shown that alpha-mannosidase and alpha-galactosidase can hydrolyse these linkages after proteolytic digestion of glucoamylase.

Adsorption of glucoamylase from Asp. awamori X-100/D27 on cell walls.

Upon secretion, the major form of glucoamylase from Asp. awamori adsorbs on fungal cell walls. Its substrate binding site showing affinity for alpha-1-4 and alpha-1-6 wall glucans is responsible for adsorption.

Refined structure for the complex of 1-deoxynojirimycin with glucoamylase from Aspergillus awamori var. X100 to 2.4-A resolution.

The three-dimensional structure of the complex of 1-deoxynojirimycin with glucoamylase II-(471) from Aspergillus awamori var. X100 has been determined to 2.4-A resolution.

Effect of modification of carbohydrate component on properties of glucoamylase.

In this study, we investigated enzymatic deglycosylation of glucoamylase from Aspergillus awamori X 100/D27, a glycoprotein which has two N-linked and about forty short mannose-bearing O-linked sugars per molecule. O-Linked sugars were modified by treatment with alpha-mannosidase and N-linked sugars were removed using endo-beta-N-acetylglucosaminidase F. Analysis of conformational changes following deglycosylation suggests that O-linked sugars essentially contribute to the stabilization of glucoamylase domains.

Crystal structure of glucoamylase from Aspergillus awamori var. X100 to 2.2-A resolution.

The crystal structure of a catalytically active fragment of glucoamylase-I from Aspergillus awamori var. X100 has been determined to a resolution of 2.2 A.

Crystallization and preliminary X-ray study of minor glucoamylase from Aspergillus awamori variant X-100/D27.

Crystals of the reduced form of glucoamylase were obtained from polyethylene glycol 6000 solution by the hanging-drop method. The protein was treated with alpha-mannosidase to partly remove the sugar component. The crystals belong to the space group P2(1)2(1)2(1) with cell dimensions a = 116.

Different neurophysiological mechanisms underlying delayed reaction and trace conditioned reflex.

Electrophysiological study of functional interactions of the prefrontal cortex, the hippocampus, the head of the caudate nucleus and the thalamic medio-dorsal nucleus in 2 monkeys in conditions of the trace reflex and delayed reaction has revealed various morphofunctional systems for these types of memory. The morphofunctional system of the trace CR is characterized by greater stability and a small number of functional connections (21%) in contrast to the dynamic morphofunctional system with a considerable percentage of functional contacts (54%) in case of the delayed reaction. This difference can be very likely related to the different dynamics of functional connections between brain structures rather than to the involvement of various brain structures.

[Behavioral characteristics of rhesus monkeys in a multiple-choice environment].

The present work deals with dynamics of formation of complex alimentary behaviour of rhesus monkeys in multialternative environment. A detailed informational analysis of the obtained results allowed to reveal the properties of processing of proprioceptive information in the course of learning and to understand the characteristics of behaviour of the examined monkeys.

Factor of selectivity in organization of complex behavior in primates.

Selectivity in the activity of the mammalian brain is examined on the basis of an analysis of a substantial experimental material obtained in our laboratory during the investigation of the conditioned reflex and delayed behavior in lower and higher primates.

[Physiological analysis of the relation between the conditioned reflex and image memory in monkeys and preschool children].

Interaction of short-term and long-term memory processes is subjected to phylo- and ontogenetic changes. Progressive development includes differentiation and independent manifestation of these memory forms together with formation of a more complex pattern of interaction between the latter.

[Role of the caudate nucleus head in delayed spatial preference and differentiation of trace reflexes in Macaca mulatta].

Using phase-correlation analysis, electrical stimulation and pharmacological treatment (Benactyzine), changes in functional importance of the head of n. caudatus have been observed which were related to regulation needs for the delayed spatial preference and differentiation of temporal reflexes. Structural elements of any morpho-functional system are not determined constantly by one and the same functional importance.

[Evolution of tool handling activity in monkeys].

Main experimental data are presented which have been obtained on lower and higher monkeys. New understanding is suggested of regularities of interaction of primates with the environmental objects. The data are discussed in relation to historic and ontogenetic development of working activity in man.

[Characteristics of the interaction of image and conditioned reflex memory during the ontogeny of chimpanzees].

Interaction of a stable conditioned reflex and trace visual image of a natural alimentary stimulus was studied in two groups of chimpanzee youngs. A. higher stability of visual imaginative memory was observed in animals of the elder group.