Search PubMed⌕ Search

Biomedical subjects

B Svensson

Publications and source records attributed to B Svensson.

At least 199 records · Page 11Linked to original sources
PubMed1990

Activity and thermal stability of genetically truncated forms of Aspergillus glucoamylase.

Glucoamylase (GA) from Aspergillus awamori (EC 3.2.1.3) is a secreted starch hydrolase with a large catalytic domain (aa 1-440), a starch-binding domain (aa 513-616), and a highly O-glycosylated region of 72 aa of unknown function that links the catalytic and starch-binding domains. We have genetically engineered a series of truncated forms of GA to determine how much of the highly O-glycosylated region is necessary for the activity or stability of GAII, a fully active form of the enzyme that lacks the starch-binding domain. Mutations were made by inserting stop-codon linkers into restriction sites within the coding region of the GA gene, and mutated genes were expressed in Saccharomyces cerevisiae for analysis of the truncated enzymes. Our results show that up to 30 aa from the C-terminal end of GAII can be deleted with little effect on the activity, thermal stability, or secretion of the enzyme. Further deletions resulted in diminution or loss of enzyme activity on starch plates, and loss of detectable enzyme in culture supernatants, indicating that these residues are essential for GAII function.

Amino Acid Sequence↗
PubMed1990

Identification of carboxylic acid residues in glucoamylase G2 from Aspergillus niger that participate in catalysis and substrate binding.

Functionally important carboxyl groups in glucoamylase G2 from Aspergillus niger were identified using a differential labelling approach which involved modification of the acarbose-inhibited enzyme with 1-ethyl-3-(4-azonia-4,4-dimethylpentyl)carbodiimide (EAC) and inactivation by [3H]EAC following removal of acarbose. Subsequent sequence localization of the substituted acidic residues was facilitated by specific phenylthiohydantoins. The acid cluster Asp176, Glu179 and Glu180 reacted exclusively with [3H]EAC, while Asp112, Asp153, Glu259 and Glu389 had incorporated both [3H]EAC and EAC. It is conceivable that one or two of the [3H]EAC-labelled side chains act in catalysis while the other fully protected residue(s) participates in substrate binding probably together with the partially protected ones. Twelve carboxyl groups that reacted with EAC in the enzyme-acarbose complex were also identified. Asp176, Glu179 and Glu180 are all invariant in fungal glucoamylases. Glu180 was tentatively identified as a catalytic group on the basis of sequence alignments to catalytic regions in isomaltase and alpha-amylase. The partially radiolabelled Asp112 corresponds in Taka-amylase A to Tyr75 situated in a substrate binding loop at a distance from the site of cleavage. A possible correlation between carbodiimide modification of an essential carboxyl group and its role in the glucoamylase catalysis is discussed.

Acarbose↗
PubMed1990

Structure of donor side components in photosystem II predicted by computer modelling.

Thirty-one and eleven sequences for the photosystem II reaction centre proteins D1 and D2 respectively, were compared to identify conserved single amino acid residues and regions in the sequences. Both proteins are highly conserved. One important difference is that the lumenal parts of the D1 protein are more conserved than the corresponding parts in the D2 protein. The three-dimensional structures around the electron donors tyrosineZ and tyrosineD on the oxidizing side of photosystem II have been predicted by computer modelling using the photosynthetic reaction centre from purple bacteria as a framework. In the model the tyrosines occupy two cavities close to the lumenal surface of the membrane. They are symmetrically arranged around the primary donor P680 and the distances between the centre of the tyrosines and the closest Mg ion in P680 are around 14 A. Both tyrosineZ and tyrosineD are suggested to form a hydrogen bond with histidine 190 from the loop connecting helices C and D in the D1 and D2 proteins, respectively. The Mn cluster in the oxygen evolving complex has been localized by using known and estimated distances from the tyrosine radicals. It is suggested that a binding region for the Mn cluster is constituted by the lumenal ends of helices A and B and the loop connecting them in the D1 protein. This part of the D1 protein contains a large number of strictly conserved carboxylic acid residues and histidines which could participate in the Mn binding. There is little probability that the Mn cluster binds on the lumenal surface of the D2 protein.

Amino Acid Sequence↗
PubMed1990

Different effects on the responses of functional pre- and postsynaptic 5-HT1A receptors by repeated treatment of rats with the 5-HT1A receptor agonist 8-OH-DPAT.

The effects of repeated treatment of rats with 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), 1.0 mg/kg, subcutaneously, twice daily for 7 days, on the stimulation of post- and presynaptic 5-HT1A receptors were examined. The postsynaptic responses, hypothermia and inhibition of the cage-leaving response, evoked by 0.05 mg/kg 8-OH-DPAT, were measured 48 hr after the final injection. Another postsynaptic response, the 5-HT syndrome (flat body posture and forepaw treading) was observed after the third injection of 8-OH-DPAT (1.0 mg/kg s.c.). One presynaptic response examined was the 8-OH-DPAT-induced decrease in the concentration of 5-hydroxyindoleacetic acid (5-HIAA), that indicates a decrease in turnover of 5-HT, due to stimulation of 5-HT receptors on the cell bodies and measured as the ratio of 5-HIAA to 5-HT in the hippocampus, hypothalamus and medulla oblongata. Another presynaptic response was the 8-OH-DPAT-induced decrease in the accumulation of 5-hydroxytryptophan (5-HTP) in the hippocampus and hypothalamus, after inhibition of L-aromatic amino acid decarboxylase by 3-hydroxybenzylhydrazine (NSD 1015), that is due to stimulation of autoreceptors on the 5-HT cell bodies. The kinetic properties of 5-HT1A receptors in the cerebral cortex and hippocampus, hippocampus alone, hypothalamus and medulla oblongata were determined with [3H]8-OH-DPAT. It was found that the postsynaptic effects were markedly attenuated after the treatment, the hypothermic effect already after a single dose.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Hydroxytryptophan↗
PubMed1990

Electrostatic contributions to the binding of Ca2+ in calbindin mutants. A Monte Carlo study.

Monte Carlo simulation is used to calculate the free energy of binding of calcium ions to the native and several mutant forms of bovine calbindin D(9K) in salt solution. The simulations are performed in the canonical ensemble wherein free energies are calculated with a modified Widom method. The protein is modelled as a set of fixed hard spheres of fractional or unit charge with the surrounding solution as a dielectric continuum containing counterions and added salt particles. The interior of the protein is assumed to have the same dielectric permittivity as the solvent, which turns out to be an excellent approximation. Indeed, this simple model is able to predict accurately experimentally measured shifts in the calcium binding constants of up to five orders of magnitude, due to mutations and added salt.

Journal Article↗
PubMed1990

Elderly people in an orthopedic emergency room--assessment of quality.

About 25% of all outpatients in the emergency room at the department of orthopedics in Malmö are over 70 years of age. Fourteen per cent had no one to ask for help at home if needed. Seventy-two per cent understood the information given them correctly. About half of the patients reported satisfaction with the consultation. Three specific problems related to the service provided were identified; a long waiting time, a limited approach to the patients' problem and a lack of follow up care.

Aged↗
PubMed1990

Catalytic mechanism of fungal glucoamylase as defined by mutagenesis of Asp176, Glu179 and Glu180 in the enzyme from Aspergillus awamori.

Asp176, Glu179 and Glu180 of Aspergillus awamori glucoamylase appeared by differential labeling to be in the active site. To test their functions, they were replaced by mutagenesis with Asn, Gln and Gln respectively, and kinetic parameters and pH dependencies of all enzyme forms were determined. Glu179----Gln glucoamylase was not active on maltose or isomaltose, while the kcat for maltoheptaose hydrolysis decreased almost 2000-fold and the KM was essentially unchanged from wild-type glucoamylase. The The Glu180----Gln mutation drastically increased the KM and moderately decreased the kcat with maltose and maltoheptaose, but affected isomaltose hydrolysis less. Difference in substrate activation energies between Glu180----Gln and wild-type glucoamylases indicate that Glu180 binds D-glucosyl residues in subsite 2. The Asp176----Asn substitution gave moderate increases and decreases in KM and kcat respectively, and therefore similar increases in activation energies for the three substrates. This and the differences in subsite binding energies between Asp176----Asn and wild-type glucoamylases suggest that Asp176 is near subsite 1, where it stabilizes the transition state and interacts with Trp120 at subsite 4. Glu179 and Asp176 are thus proposed as the general catalytic acid and base of pKa 5.9 and 2.7 respectively. The charged Glu180 contributes to the high pKa value of Glu179.

Amino Acid Sequence↗
PubMed1990

Disease activity and joint damage progression in early rheumatoid arthritis: relation to IgG, IgA, and IgM rheumatoid factor.

The clinical and biochemical correlations with joint damage progression over two years in a consecutive group of 68 patients with rheumatoid arthritis with disease duration of less than two years are reported. Joint damage was assessed with Larsen's severity scale and a measure of change in progression rate constructed. Initial haemoglobin concentration, Ritchie index, and Waaler-Rose titre in combination accounted for one third of the variance in joint damage progression. Rheumatoid factor (RF) concentrations were followed with enzyme linked immunosorbent assays (ELISAs) for IgG RF, IgA RF, and IgM RF. The RF concentrations, except IgG RF, decreased with time; significant correlations between RFs and disease activity were few and barely clinically useful. After two years IgG RF correlated significantly with a radiological score if early non-erosive changes were omitted. All RFs tended to correlate better with this radiological score at all three observation points. Analyses of the change in progression rate indicated a time delay between development of radiographic changes and increase of IgG RF. These results suggest an indirect relation between RFs and joint damage. Clinical and biochemical improvements in early RA occur despite joint damage progression, and conventional markers have insufficient predictive value.

Arthritis, Rheumatoid↗
PubMed1990

Female sex hormones and platelet/endothelial cell interactions.

The effects of estradiol and progesterone added to the growth medium of human umbilical vein endothelial cells for 72 h on the formation and release of prostacyclin were investigated. The influence on collagen-induced platelet aggregation and on the platelet formation of thromboxane A2 following aggregation, of the growth medium collected before and after thrombin stimulation of the endothelial cells, was studied simultaneously. Under basal conditions, endothelial cells grown with progesterone released significantly less prostacyclin into the growth medium than did controls (p less than 0.05). Following thrombin stimulation, endothelial cells grown with estradiol (p less than 0.05) or a combination of estradiol and progesterone (p less than 0.01) contained significantly less prostacyclin than controls. No significant effects on the platelet aggregation or platelet thromboxane formation could be found. This study indicates a lowering effect of both female sex hormones on the endothelial cell prostacyclin formation and release. This may be of significance for the increased risk of vascular disease in pregnant women and oral contraceptive users, but can hardly explain the consequences of the hormonal loss occurring at the menopause.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Dynamic versus static training in patients with rheumatoid arthritis.

Sixty-seven patients with classical or definite rheumatoid arthritis (RA) were studied concerning the effects of standardized physical training on muscle function in the lower extremities. The patients were randomly assigned to four different training groups and were given 6 weeks of training supervised by a physiotherapist at a health care centre. The groups differed according to type (dynamic or static) and extent (12 or 4 times) of training. During this training period as well as for an additional 3 months, the patients carried out programs of exercise at home (either dynamic or static). A significantly greater increase in function during the 6-week period as regards muscle strength, endurance, aerobic capacity, and functional ability was found for the dynamic as compared with the static groups. The findings at follow-up 3 months later were similar. The effectiveness of the programs did not vary with the extent of training. In conclusion, in RA patients, dynamic training gives a greater increase in physical capacity than does static training.

Activities of Daily Living↗
PubMed1989

The effect of lipopolysaccharides (LPS) on generation of thromboxane A2 and thromboplastin activity in whole blood of males, females and females on oral contraceptives.

Heparinized blood sample taken from 81 healthy persons, 40 men and 41 women of whom 17 were on combined oral contraceptives, were incubated with 2 ng lipopolysaccharides (LPS)/ml blood. Quantitation of thromboxane B2 (TxB2) in the resultant plasma revealed a significantly (p less than 0.001) higher generation of TxB2 in men than in women. No sexual differences were observed in thromboplastin activity in unstimulated and LPS stimulated monocytes. Addition of liposomes together with LPS enhanced the synthesis of thromboplastin 2-10 fold and unveiled a higher synthesis of thromboplastin among men. No differences were observed in TxB2 and thromboplastin synthesis in blood collected from females or females using oral contraceptives. A significant correlation between TxB2 and the thromboplastin activity exists within the male (r = 0.46, p = 0.003) and the oral contraceptive (r = 0.57, p = 0.016) group after exposure to LPS. This study suggests that males exposed to LPS may generate more thromboxane A2 than females and thus be at higher risk of developing thrombosis.

Adult↗
PubMed1989

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.

Amino Acid Sequence↗
PubMed1989

A 39 kD barley seed protein of the serpin superfamily inhibits alpha-chymotrypsin.

A 39 kD protein has been extracted from barley flour with 0.1 M monothioglycerol at pH 5.0 and purified by (NH4)2SO4-precipitation, anion exchange and molecular sieve chromatography. It is an N-terminally blocked, non-glycosylated, single-chain protein present in at least two molecular forms of isoelectric points 5.18 and 5.22. The amino acid composition and partial sequence analysis reveal a relationship to barley endosperm Z protein which belongs to the serpin superfamily. The 39 kD protein inhibits alpha-chymotrypsin while little or no effect could be demonstrated on trypsin, subtilisin, proteinase K, S. aureus V8 protease, thermolysin or two malt thiol endoproteinases. The 39 kD protein is immunochemically related to the major protein component in beer.

Amino Acid Sequence↗
PubMed1989

Side chain reactivities of glucoamylase G2 from Aspergillus niger evaluated by group-specific chemical modifications.

Treatment of glucoamylase G2 with large excesses of different group specific reagents resulted in modification of 25% of the histidyl, 15% of the tyrosyl, 20-40% of the arginyl, 30-50% of the lysyl and none of the methionyl residues. The modified groups were not critical since the various derivatives possessed from 50% to 100% residual enzymatic activity and retained the thermostability. Carboxamidomethylation occurred specifically at His254 with essentially no change of the kinetic parameters for hydrolysis of maltose and starch. Removal of the two N-linked sugar units by endoglycosidase H was similarly without effect on activity, thermostability and chemical reactivity of the histidyl residues. H(+)-titration revealed that glucoamylase G2 carries a lower net charge throughout the pH-range 3-11 than predicted from its amino acid composition.

Acetylglucosaminidase↗
PubMed1989

Muscle function of the lower extremities in rheumatoid arthritis and osteoarthrosis. A descriptive study of patients in a primary health care district.

Thirty-six patients with rheumatoid arthritis (RA), 30 patients with cox- or gonarthrosis (OA), and a control group of 40 patients with diabetes mellitus (DM) were studied with the aim of analyzing and comparing patient experienced muscular problems of muscle-strength analyzing and comparing patient experienced muscular problems of muscle-strength, endurance and balance/coordination with muscle function as assessed by standardized tests. The results indicated that patient-experienced problems of muscle function of the lower extremities were frequent in both the RA and the OA groups (about 80%) compared to the DM group (10%). Multivariate analyses of variance (MANOVAs) on experienced and tested muscle strength, endurance and balance/coordination, revealed a significant RA-OA difference (p less than 0.05). Separate analyses of variance (ANOVAs) indicated OA patients to show decreased tested endurance compared with the RA group. There was no significant RA-OA difference as to pain. Results provide evidence for considering muscle function of the lower extremities in therapeutic programs for RA and OA within primary health care.

Activities of Daily Living↗