Biomedical subjects

B Svensson

Publications and source records attributed to B Svensson.

At least 145 records · Page 8Linked to original sources

PubMed1994

Domain B protruding at the third beta strand of the alpha/beta barrel in barley alpha-amylase confers distinct isozyme-specific properties.

alpha-Amylases belong to the alpha/beta-barrel protein family in which the active site is created by residues located at the C-terminus of the beta strands and in the helix-connecting loops extending from these ends. In the alpha-amylase family, a small separate domain B protrudes at the C-terminus of the third beta strand of the (beta/alpha)8-barrel framework. The 80% identical barley alpha-amylase isozymes 1 and 2 (AMY1 and AMY2, respectively) differ in substrate affinity and turnover rate, CaCl2 stimulation of activity, sensitivity to the endogenous 21-kDa alpha-amylase/subtilisin inhibitor, and stability at low pH. To identify regions that confer these isozyme-specific variations, AMY1-AMY2 hybrid cDNAs were generated by in vivo homologous recombination in yeast. The hybrids AMY1-(1-90)-AMY2-(90-403) and AMY1-(1-161)-AMY2-(161-403) characterized in this study contain the 90-residue and 161-residue N-terminal sequences, respectively, of AMY1 and complementary C-terminal regions of AMY2. AMY1-(1-90)-AMY2-(90-403) comprises the 60-amino-acid domain B of AMY2 and resembles this isozyme in sensitivity to alpha-amylase/subtilisin inhibitor and its low affinity for the substrates p-nitrophenyl alpha-D-maltoheptaoside, amylose and the inhibitor acarbose. Only AMY1-(1-161)-AMY2-(161-403) and AMY1, which both share domain B, are stable at low pH. However, AMY2 and both hybrid AMY species, but not AMY1, show maximum enzyme activity on insoluble blue starch at approximately 10 mM CaCl2. Domain B thus determines several functional and stability properties that distinguish the barley alpha-amylase isozymes.

Acarbose↗

PubMed1994

Characterization, crystallization and preliminary X-ray crystallographic analysis of the complex between barley alpha-amylase and the bifunctional alpha-amylase/subtilisin inhibitor from barley seeds.

The complex between a member of the barley malt alpha-amylase isozyme 2 family (AMY2-2), and the endogenous bifunctional alpha-amylase/subtilisin inhibitor, BASI, has been crystallized by the hanging drop vapour diffusion technique at a AMY2-2: BASI molar ratio of 1:1. Crystals have been grown within 4 days from solutions containing polyethylene glycol and calcium chloride. Analysis of single crystals by gel electrophoresis showed the presence of both proteins in the crystal lattice. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell dimensions a = 74.5 A, b = 96.9 A, c = 171.3 A and they diffract to 2.0 A resolution. The presence of two molecules of the 1:1 complex in the asymmetric unit gives a solvent content of 45% by volume. The 1:1 stoichiometry of the complex was confirmed by the molecular replacement method, using as a search model the recently determined three-dimensional structure of the barley alpha-amylase.

Crystallization↗

PubMed1994

Localization of an O-glycosylated site in the recombinant barley alpha-amylase 1 produced in yeast and correction of the amino acid sequence using matrix-assisted laser desorption/ionization mass spectrometry of peptide mixtures.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of peptide mixtures was used to characterize recombinant barley alpha-amylase 1, produced in yeast. Three peptide mixtures were generated by cleavage with CNBr, digestion with endoproteinase Lys-C and Asp-N, respectively, and analyzed directly by MALDI-MS. Based on the three mass spectrometric peptide maps, an error in the sequence deduced from cDNA, resulting in a mass difference of 28 Da, was located to a sequence stretch of 5 amino acid residues; furthermore, a dihexose substituent was identified on Thr410. Subsequent Edman degradation of two selected peptides isolated from the endoproteinase Lys-C digest corrected the sequence to be Val instead of Ala in position 284 and confirmed the O-glycosylation. These results demonstrate that the direct peptide mixture analysis by MALDI-MS is a rapid and sensitive method for protein characterization and provides valuable information before further characterization.

Amino Acid Sequence↗

PubMed1994

Protein engineering in the alpha-amylase family: catalytic mechanism, substrate specificity, and stability.

Most starch hydrolases and related enzymes belong to the alpha-amylase family which contains a characteristic catalytic (beta/alpha)8-barrel domain. Currently known primary structures that have sequence similarities represent 18 different specificities, including starch branching enzyme. Crystal structures have been reported in three of these enzyme classes: the alpha-amylases, the cyclodextrin glucanotransferases, and the oligo-1,6-glucosidases. Throughout the alpha-amylase family, only eight amino acid residues are invariant, seven at the active site and a glycine in a short turn. However, comparison of three-dimensional models with a multiple sequence alignment suggests that the diversity in specificity arises by variation in substrate binding at the beta-->alpha loops. Designed mutations thus have enhanced transferase activity and altered the oligosaccharide product patterns of alpha-amylases, changed the distribution of alpha-, beta- and gamma-cyclodextrin production by cyclodextrin glucanotransferases, and shifted the relative alpha-1,4:alpha-1,6 dual-bond specificity of neopullulanase. Barley alpha-amylase isozyme hybrids and Bacillus alpha-amylases demonstrate the impact of a small domain B protruding from the (beta/alpha)8-scaffold on the function and stability. Prospects for rational engineering in this family include important members of plant origin, such as alpha-amylase, starch branching and debranching enzymes, and amylomaltase.

Amino Acid Sequence↗

PubMed1994

Health benefits from a layman intervention in the primary health care.

In order to make a necessary life-style change, it is of the utmost importance that a sound motivation is created and the best help a person can get in the process of change is social support. The aim of this study was to locate people having physical symptoms of ill-being and to evaluate the work of a primary prevention programme, especially with regard to health benefits. The sample for the study was made up of 134 consecutive patients who went to see a health care professional because they had subjective complaints. The patients were offered a keep-fit exercise programme, i.e. a layman intervention of an educative-supportive nature, which consisted of ten assignments in a fitness club. The assignments comprised both physical exercise and psychosocial instructions. Two self-rated questionnaires were to be filled in; one at the beginning of the intervention and the other 1 year after its completion. Demographic data focused the attention on a female, manual, middle-aged worker, having symptoms bearing on the musculoskeletal system. The intervention definitely affected the life-style, thus favourably changing physical, psychosocial, and behavioural variables (e.g. increased physical well-being t-test: P < 0.001; decreased stress, t-test: P < 0.001; increased physical events, t-test: P < 0.01). In plain language, the use of the said intervention can result in the patients taking less time on sick-relief. Therefore, if many more people could be encouraged to take part in intervention programmes, the national medical cost would most likely be reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Protein engineering of the relative specificity of glucoamylase from Aspergillus awamori based on sequence similarities between starch-degrading enzymes.

Aspergillus glucoamylase catalyzes hydrolysis of D-glucose from non-reducing ends of starch with an approximately 300-fold (kcat/Km) preference for the alpha-1,4- over the alpha-1,6-glucosidic linkage determined using the substrates maltose and isomaltose. It is postulated that as most amylolytic enzymes act on either the alpha-1,4- or alpha-1,6-linkages, sequence comparison between active-site regions should enable the correlation of the substrate bond specificity with particular residues at key positions. Therefore, the already high bond-type selectivity in Aspergillus glucoamylase could theoretically be augmented further by three single mutations, Ser119-->Tyr, Gly183-->Lys and Ser184-->His, in two separate active-site regions. These mutants all had slight increases in activity as compared with the wild-type enzyme towards the alpha-1,4-linked maltose; this was due to lower Km values as well as small decreases in activity towards isomaltose. This latter decrease in activity was a result of higher Km values and a decrease in kcat for the Ser184-->His mutant. As a consequence, the selectivity of the three glucoamylase mutants for alpha-1,4- over alpha-1,6-linked disaccharides is enhanced 2.3- to 3.5-fold. In addition, the introduction of a cationic side chain in Gly183-->Lys and Ser184-->His glucoamylase, broadens the optimal pH range for activity towards acidic as well as alkaline conditions.

Amino Acid Sequence↗

PubMed1994

Endurance training in patients with multiple sclerosis: five case studies.

BACKGROUND AND PURPOSE: The purpose of this report is to describe how patients with multiple sclerosis increased the isokinetic peak torque of their knee flexors and perceived well-being after an endurance training program. SUBJECTS AND METHODS: Five patients trained for 4 to 6 weeks using an endurance program for the lower extremities. Before and after training, the subjects performed 50 repeated maximum knee flexions, with simultaneous recording of surface electromyographic activity of two knee flexors, on 3 separate days using an isokinetic dynamometer. Throughout the tests, the subjects rated their perception of peripheral muscle fatigue. Visual analog scales (VAS) were used to rate different aspects of well-being. RESULTS: Both the perception of peripheral fatigue and the different VAS ratings had changed positively after training. Three patients achieved higher peak torque levels throughout the posttraining endurance test. CONCLUSION AND DISCUSSION: Based on these positive results, the authors conclude that more comprehensive studies of exercise prescription in patients with multiple sclerosis are desirable.

Activities of Daily Living↗

PubMed1994

Basal plasma concentration of tissue plasminogen activator (t-PA) and the adaption to strenuous exercise in familial hypercholesterolaemia (FH).

Epidemiological studies have provided evidence that attenuated fibrinolytic activity and increased antigen levels of plasminogen activator are risk factors for coronary heart disease (CHD). In a comparative study, tissue plasminogen activator (t-PA) antigen and activity concentrations were examined in plasma from familial hypercholesterolaemia (FH) patients without manifest CHD (n = 14) and in age- and sex-matched normolipaemic controls (NLC) at rest and after the same bicycle exercise. The FH patients had higher systolic and diastolic blood pressure than their controls. The plasma level of t-PA antigen was higher in FH patients than in NLC under basal conditions (7.3 +/- 3.1 ng/ml vs 4.8 +/- 2.2 ng/ml, P = 0.022), whereas no difference was found in t-PA activity. Bicycle exercise induced a marked increase in t-PA antigen (P < 0.001 for both groups) which did not differ between groups. A more prominent rise in t-PA activity was observed among the FH patients during the exercise (1.71 +/- 0.99 vs 0.85 +/- 0.89 IU/ml, P = 0.24). Neither the basal level of thrombin-antithrombin III complex (TAT) nor the significant increase (P < 0.001 for both groups) induced by exercise differed between groups. A high t-PA antigen level may precede clinical manifestations of cardiovascular disease in patients with familial hypercholesterolaemia.

Adaptation, Physiological↗

PubMed1994

Patient satisfaction with inpatient psychiatric care. The influence of personality traits, diagnosis and perceived coercion.

The aim of the study was to investigate the influence of personality traits, diagnosis and perceived coercion on patient satisfaction with inpatient psychiatric care. The study was performed as a cross-sectional study on 7 inpatient wards in southern Sweden. A cohort of 50 psychiatric inpatients evaluated satisfaction with care and also made ratings on a personality questionnaire. Patients with a higher level of the trait aggressive nonconformity were significantly less satisfied with the ward's physical and psychosocial environment, the treatment design and the treatment program. The phenomenon of acquiescence was not related to the reported level of satisfaction. Analyses of patient satisfaction according to diagnostic groups showed that patients with affective disorders had significantly better satisfaction than patients with a diagnosis of schizophrenia. Patients who perceived that they were involuntarily admitted were measured as being significantly less satisfied with the care in all areas. It is concluded that, to attain a higher specificity in analyses of variation in patient satisfaction, focus may be put on situational and setting factors of the care delivered along with specific patient characteristics. Risk groups, which require great attention in the development of quality assessment and quality assurance policies, are patients with schizophrenia and patients who perceive coercion in connection with inpatient psychiatric treatment.

Adolescent↗

PubMed1994

Bacillus subtilis CtaA is a heme-containing membrane protein involved in heme A biosynthesis.

Heme A is a prosthetic group of many respiratory oxidases. It is synthesized from protoheme IX (heme B) seemingly with heme O as a stable intermediate. The Bacillus subtilis ctaA and ctaB genes are required for heme A and heme O synthesis, respectively (B. Svensson, M. Lübben, and L. Hederstedt, Mol. Microbiol. 10:193-201, 1993). Tentatively, CtaA is involved in the monooxygenation and oxidation of the methyl side group on porphyrin ring D in heme A synthesis from heme B. B. subtilis ctaA and ctaB on plasmids in both B. subtilis and Escherichia coli were found to result in a novel membrane-bound heme-containing protein with the characteristics of a low-spin b-type cytochrome. It can be reduced via the respiratory chain, and in the reduced state it shows light absorption maxima at 428, 528, and 558 nm and the alpha-band is split. Purified cytochrome isolated from both B. subtilis and E. coli membranes contained one polypeptide identified as CtaA by amino acid sequence analysis, about 0.2 mol of heme B per mol of polypeptide, and small amounts of heme A.

Amino Acid Sequence↗

PubMed1994

Tissue-factor pathway inhibitor and lipoproteins. Evidence for association with and regulation by LDL in human plasma.

Tissue-factor pathway inhibitor (TFPI) is a potent inhibitor of extrinsic coagulation, which is mainly associated with lipoproteins in circulating blood. Gel filtration of human plasma confirmed the presence of three peaks in which approximately 10%, 70%, and 20% of total TFPI activity was retained. Precipitation of very-low-density lipoproteins and low-density lipoproteins (LDLs) in plasma by polyethylene glycol almost completely abolished peaks and I and II. LDL isolated by ultracentrifugation revealed two peaks of TFPI after gel filtration that coeluted with peaks I and II, respectively, from gel filtration of total plasma. TFPI activity in peaks I and II was also precipitated by anti-apolipoprotein B antibodies. Fourteen patients with familial hypercholesterolemia had higher plasma TFPI activity than did age- and sex-matched normolipemic control subjects (1.45 +/- 0.27 U/mL versus 0.80 +/- 0.09 U/mL, P < .001). Plasma TFPI was correlated with LDL cholesterol (r = .73, P < .001) and apolipoprotein B (r = .69, P < .001). No association was found with high-density lipoprotein cholesterol or apolipoprotein A-I. In a double-blind, placebo-controlled trial among the familial hypercholesterolemia patients, lovastatin alone or in combination with fish oil concentrate lowered plasma TFPI in parallel with LDL cholesterol. Gel filtration of plasma from these patients demonstrated a specific drop in apolipoprotein B-TFPI complexes, whereas TFPI not associated with lipoproteins was unchanged. This study demonstrated that plasma TFPI was associated with and regulated by LDL in plasma from healthy subjects and patients with familial hypercholesterolemia.

Adult↗

PubMed1994

Phaco-emulsification causes the formation of cavitation bubbles.

There have been reports of complications arising from damage to non-lenticular ocular tissue during the increasingly popular procedure of cataract extraction with phaco-emulsification. One cause of this damage might be the formation of cavitation bubbles. Such bubbles are known to produce free radicals and shock waves. This paper demonstrates directly the formation of cavitation bubbles at the tip of the phaco-probe. It also shows the importance of a smooth probe profile in reducing bubble formation. Recommendations are made for probe and tip design and for the use of minimum power during the surgical procedure of phaco-emulsification.

Cataract Extraction↗

PubMed1994

Dynamic training and circulating neuropeptides in patients with rheumatoid arthritis: a comparative study with healthy subjects.

This study aimed at evaluating the effects of a dynamic physical training programme on circulating levels of corticotropin-releasing hormone (CRH), beta-lipotropin (beta-LPH), and beta-endorphin (beta-EP) after high-intensity training for 6 weeks (60 min twice a week) and after low-intensity training (home-training) for another 6 months in patients with rheumatoid arthritis (RA) and in healthy subjects. Additionally, differences in neuropeptide levels between the two groups were studied. A total of 30 patients with RA were randomly allocated to the study, 15 in the training group (TG) and 15 in the control group (CG). In addition, 20 healthy subjects (10 in TG; 10 in CG) participated. In addition to the biochemical analyses, the following variables were assessed for the RA group: pain and disability (Stanford health assessment questionnaire), joint tenderness (Ritchie articular index), disease activity, muscle function, aerobic capacity, sociodemographic data and attitudes. The results obtained at the start revealed significant differences (p < 0.05) between RA patients and healthy subjects concerning CRH levels, RA patients showing the lower levels (RA-group Md = 24 pmol/L, healthy group Md = 29 pmol/L). No significant differences concerning beta-LPH and beta-EP were found here. After the high-intensity training period, a significant increase of the CRH levels were found for the RA-TG (pretest Md = 24 pmol/L, after 6 weeks Md = 27 pmol/L, p < 0.05). No such results were found for the healthy-TG or the control groups. Concerning beta-EP, significant differences between the RA-TG and healthy-TG were found after the training. RA patients generally showing higher levels as compared with the healthy (RA-group Md = 42 pmol/L, healthy group Md = 36 pmol/L, p < 0.05). The same pattern was found for the beta-LPH levels. In conclusion, the effects of physical training on circulating neuropeptides remain still incompletely examined, and there is no definite answer to the question whether increased beta-EP levels are good or bad.

Adult↗

PubMed1994

[Structured assessment of the treatment of rheumatoid arthritis].

As prognosis in rheumatoid arthritis has been shown to be much poorer than formerly believed, new treatment strategies have been proposed. However, trials of these strategies require improved evaluation of their effect on the disease course and its consequences for the patient. International guidelines and a Swedish model for such evaluation are presented in the article.

Arthritis, Rheumatoid↗

PubMed1993

Lipopolysaccharide induced monocyte thromboplastin synthesis and coagulation responses in patients undergoing coronary bypass surgery after preoperative supplementation with n-3 fatty acids.

Twenty patients with coronary heart disease (CHD) and elevated serum lipids were randomized into 2 groups of 10 to receive encapsulated preparations of either a concentrated ethylester form of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) or corn oil in doses of 6 g per day, given double blindly for approximately two months prior to coronary bypass surgery. Lipopolysaccharide (LPS) induced monocyte thromboplastin synthesis was studied during the preoperative period and one week following surgery. The ability of n-3 fatty acids to modify tissue factor pathway inhibitor (TFPI) and tissue plasminogen activator inhibitor (PAI-1) was also evaluated along with fibrinogen and thrombin-antithrombin III (TAT) complexes. No significant changes were noted preoperatively. Monocyte reactivity, PAI-1, fibrinogen and TAT increased significantly after surgery. These changes were not modified by preoperative loading with n-3 fatty acids.

Acute-Phase Reaction↗

PubMed1993

Site-directed mutagenesis of histidine 93, aspartic acid 180, glutamic acid 205, histidine 290, and aspartic acid 291 at the active site and tryptophan 279 at the raw starch binding site in barley alpha-amylase 1.

The pseudotetrasaccharide acarbose has high affinity for the active site (Ki,app = 1 microM) and low affinity for a secondary site (Kd = 2.3 mM) in barley alpha-amylase 1, distinguished by inhibition kinetics and spectral perturbation. Mutants of putative catalytic residues, D180N, E205Q, and D291N, are inactive and display low affinity for acarbose-Sepharose. H93N and H290N mutants, at invariant residues, have kcat/Km for p-nitrophenylmaltoheptaoside of 0.3 and 1.2% of wild-type. A corresponding 370- and 85-fold increased Ki,app for acarbose and a lack of shifts in pH activity profiles indicate that these histidines participate in transition state stabilization but not directly in catalysis. This finding agrees with H bonding to OH groups of the valienamine ring of acarbose in the three-dimensional structure. Loss of inhibition above pH 6 supports that acarbose is most potent in protonated form. The low affinity site contains Trp278 and Trp279, known to bind cyclomaltoheptaose. While the W279A mutant has 10-fold decreased affinity for starch granules, production of Trp278 mutants failed. The invariant Trp278 is perhaps critical for stability or folding in cereal alpha-amylases.

Amino Acid Sequence↗

PubMed1993

Reaction mechanisms of Trp120-->Phe and wild-type glucoamylases from Aspergillus niger. Interactions with maltooligodextrins and acarbose.

Interactions of wild-type and Trp120-->Phe glucoamylase with maltooligodextrin (Gx) substrates and the tight-binding inhibitor acarbose (A) were investigated here using stopped-flow fluorescence spectroscopy and steady-state kinetic measurements. All wild-type and Trp120-->Phe glucoamylase reactions followed the three-step model E + Gx(or A) (k1) <==> (k-1) EGx (or A) (k2) <==> (k-2) E*Gx(or A) (k3) --> E + P or E-A, previously shown to account for the glucoamylase-maltose system [Olsen, K., Svensson, B., & Christensen, U. (1992) Eur. J. Biochem. 209, 777-784]. K1 = k-1/k1, k2, and k-2, and the catalytic constant, k3, are determined. Binding of maltooligodextrins in the first reaction step is weak, with little difference between wild-type and Trp120-->Phe glucoamylase. The second step, involving a conformational change, in contrast, is strongly influenced by the mutation and by the substrate length. Here wild-type glucoamylase reacts faster and forms more stable intermediates the longer the substrate. In contrast, Trp120-->Phe reacts slower the longer the substrate. The effect of the mutation is thus smallest on maltose. The Trp120-->Phe substitution reduces the fluorescence signal only by 12-20%, indicating that other tryptophanyl residues are important in reporting the conformational change. Trp120 also strongly influences the actual catalytic step, since the mutation decreases the kc values 30-80-fold. Acarbose behaves similar to maltotetraose in the first and the second steps with wild-type but not the Trp120-->Phe glucoamylase. Also, a third step in the acarbose reaction which parallels the catalytic step is strongly affected by the mutation. The rate constant k3 increases 200-fold.

Acarbose↗

PubMed1993

Comparison of barley malt alpha-amylase isozymes 1 and 2: construction of cDNA hybrids by in vivo recombination and their expression in yeast.

Germinating barley produces two alpha-amylase isozymes, AMY1 and AMY2, having 80% amino acid (aa) sequence identity and differing with respect to a number of functional properties. Recombinant AMY1 (re-AMY1) and AMY2 (re-AMY2) are produced in yeast, but whereas all re-AMY1 is secreted, re-AMY2 accumulates within the cell and only traces are secreted. Expression of AMY1::AMY2 hybrid cDNAs may provide a means of understanding the difference in secretion efficiency between the two isozymes. Here, the efficient homologous recombination system of the yeast, Saccharomyces cerevisiae, was used to generate hybrids of barley AMY with the N-terminal portion derived from AMY1, including the signal peptide (SP), and the C-terminal portion from AMY2. Hybrid cDNAs were thus generated that encode either the SP alone, or the SP followed by the N-terminal 21, 26, 53, 67 or 90 aa from AMY1 and the complementary C-terminal sequences from AMY2. Larger amounts of re-AMY are secreted by hybrids containing, in addition to the SP, 53 or more aa of AMY1. In contrast, only traces of re-AMY are secreted for hybrids having 26 or fewer aa of AMY1. In this case, re-AMY hybrid accumulates intracellularly. Transformants secreting hybrid enzymes also accumulated some re-AMY within the cell. The AMY1 SP, therefore, does not ensure re-AMY2 secretion and a certain portion of the N-terminal sequence of AMY1 is required for secretion of a re-AMY1::AMY2 hybrid.

Amino Acid Sequence↗