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Biomedical subjects

N Kalkkinen

Publications and source records attributed to N Kalkkinen.

At least 19 recordsLinked to original sources
PubMed1995

Characterization, subsite mapping and partial amino acid sequence of glucoamylase from the filamentous fungus Trichoderma reesei.

The pH optimum, temperature-dependence, thermal stability, substrate specificity and subsite affinities of the 66 kDa, pI 4.0 glucoamylase of the filamentous fungus Trichoderma reesei were determined. It had a pH optimum of 5.5 and a temperature optimum (5 min reaction time) of 70 degrees C with soluble starch as substrate. Thermal-inactivation studies revealed that the glucoamylase is relatively thermostable up to 60 degrees C. Metal ions and EDTA tested at 5 mM concentrations had no significant effect, and beta-cyclodextrin only slightly inhibitory effects, on the digestion of soluble starch. Estimated Km and kcat. values for soluble starch where 0.11 mg.ml-1 and 28.5 s-1 respectively. Hydrolysis of pullulan (Km 14 mg.ml-1 and kcat. = 6.6 s-1) indicated substantial activity towards 1,6-O-glucosidic bonds. From ratios of kinetic parameters of malto- and isomalto-oligosaccharides, it was apparent that the glucoamylase showed approx. 3-fold higher selectivity towards isomalto-oligosaccharides than most other reported fungal glucoamylases. Substrate binding affinities were calculated from kinetic data for the linear series of malto- and isomalto-oligosaccharides. The results were in good agreement with other reported glucoamylases. The main difference was that subsite 1 showed a slightly negative free energy of binding with malto-oligosaccharides, whereas most other glucoamylases show a positive free energy at this subsite. A set of peptides obtained from purified glucoamylase by tryptic digestion where sequenced. They covered approx. 17% of the total amino acid sequence as estimated from molecular mass on SDS/PAGE. Some of the sequences were tentatively aligned to known glucoamylase sequences. They showed about 60% identity with the extensively studied Aspergillus glucoamylase.

Amino Acid Sequence↗
PubMed1995

Purification and characterization of different molecular forms of prostate-specific antigen in human seminal fluid.

We have developed a new procedure for purifying prostate-specific antigen (PSA) from human seminal fluid. The method is based on ammonium sulfate precipitation, hydrophobic interaction chromatography, gel filtration, and anion-exchange chromatography. It can be completed within 2 days with a recovery of intact PSA of 30%. By anion-exchange chromatography, five isoforms of PSA (A, B, C, D, and E) can be separated. The major form (PSA-B) consists of the intact enzyme, as shown by the occurrence of only one band of 33 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing or nonreducing conditions, and by amino acid sequencing, which reveals only one amino-terminal sequence corresponding to the reported amino-terminal sequence of intact PSA. The specific absorbance of 1 g/L PSA-B at 280 nm was 1.61, and 80% of the PSA-B formed a complex with alpha 1-antichymotrypsin, indicating that it is enzymatically active. Three cleaved forms of PSA with different nicking sites and low enzymatic activity were separated from intact PSA by ion-exchange chromatography. In addition, we isolated a glycosylation variant, PSA-A, which showed a higher isoelectric point (pI = 7.2) than PSA-B (pI = 6.9) but similar enzymatic activity; this form accounts for 5-10% of total PSA. After treatment with sialidase, PSA-A and B had the same isoelectric point value (pI = 7.7).

Amino Acid Sequence↗
PubMed1995

Two alpha-chain hemoglobin variants, Hb Broussais and Hb Cemenelum, characterized by cation-exchange HPLC, isoelectric focusing, and peptide sequencing.

We here report the characteristics of two rare alpha-chain hemoglobin (Hb) variants. The variants were found during quantification of HbA1c by cation-exchange HPLC with the Diamat glycohemoglobin analyzer. They were further characterized by isoelectric focusing and PolyCAT A cation-exchange chromatography. The structure of the abnormal Hbs was established by amino acid analysis after separation of the globin chains by reversed-phase chromatography, digestion with trypsin, separation of the peptides by reversed-phase chromatography, and amino acid sequencing. These studies showed that the two variants were Hb Broussais [alpha 90 (FG2)Lys-->Asn] and Hb Cemenelum [alpha 92 (FG4)Arg-->Trp].

Adolescent↗
PubMed1992

A distinct picornavirus group identified by sequence analysis.

Although echovirus 22 is presently classified as a member of the enterovirus group in the family of picornaviruses, it has been reported to have exceptional biological properties when compared with other representatives of the group. We have determined the complete nucleotide sequence of the echovirus 22 (Harris strain) genome, which appears to be significantly different from all the other studied picornaviruses. However, the organization of the genome [7339 nucleotides, excluding the poly(A) tract] is similar to that of previously sequenced picornaviruses. This genome includes a 5' untranslated region, relatively well-conserved when compared with aphtho- and cardioviruses, followed by an open reading frame coding for a 2180-amino acid-long polyprotein. The amino termini of capsid polypeptides VP1 and VP3 were determined by direct sequencing, and the other proteolytic cleavage sites in the polyprotein were predicted by comparison with other picornavirus proteins. The amino acid identities of echovirus 22 polypeptides with the corresponding proteins of other picornaviruses are in the 14-35% range, similar to those percentages seen when representatives of the five picornavirus groups (entero-, rhino-, cardio-, aphtho-, and hepatoviruses) are compared. Our results suggest that echovirus 22 belongs to an independent group of picornaviruses.

Amino Acid Sequence↗
PubMed1992

Expression of recombinant soluble and membrane-bound catechol O-methyltransferase in eukaryotic cells and identification of the respective enzymes in rat brain.

The rat and human recombinant soluble and membrane-bound catechol O-methyltransferase (S- and MB-COMT, respectively) were expressed using mammalian and baculovirus vectors. Low levels of rat and human S-COMT polypeptides were detected by immunoprecipitation in K-562 cell lines transfected with the S-COMT vectors. From K-562 cells transfected with the rat MB-COMT construct, both S- and MB-COMT recombinant proteins were detected by a rat COMT-specific anti-serum. Infection of lepidopteran Spodoptera frugiperda cells with recombinant S- or MB-COMT baculovirus constructs yielded high amounts of enzymically active and immunoreactive S- or MB-COMT proteins, respectively. Pulse/chase experiments with [35S]methionine-labelled insect cells infected with the MB-COMT baculovirus showed that the 30-kDa recombinant human MB-COMT polypeptide was not processed into the 25-kDa S-COMT form. Subcellular fractionations of insect cells, followed by immunoblotting with COMT antiserum, showed that recombinant S-COMT was found only in the soluble, cytoplasmic fraction, whereas MB-COMT resided both in soluble and membrane fractions. The recombinant MB-COMT sedimented in Percoll gradients at the density of 1.042 g/ml cosedimenting with the plasma-membrane marker. Fractionation and immunoblotting experiments on homogenized total rat brains indicated that the rat S-COMT (24 kDa) and some of the rat MB-COMT (28 kDa) was recovered in soluble fractions, whereas the microsomal material having COMT activity contained the MB-COMT polypeptide. The rat brain microsomal MB-COMT had a density of 1.042 g/ml in Percoll gradients, cosedimenting with the plasma-membrane and rough-endoplasmic-reticulum marker enzymes. The meta/para methylation ratio of dihydroxybenzoic-acid substrate by different recombinant and rat brain COMT-containing subcellular fractions was analysed.

Animals↗
PubMed1992

A heat shock gene from Saccharomyces cerevisiae encoding a secretory glycoprotein.

We report the finding of a secretory heat shock protein, HSP150, of Saccharomyces cerevisiae, and the characterization of the gene coding for it. HSP150 is constitutively expressed, extensively O-glycosylated, and secreted efficiently to the growth medium. When cells grown at 25 degrees C were shifted to 37 degrees C, a 7-fold increase in the level of HSP150 was observed within 1 hr. The HSP150 gene encodes a primary translation product of 412 amino acids. Direct amino acid sequencing of the mature secreted protein showed that an N-terminal sequence of 18 amino acids is removed, and a KEX2 protease-specific site is cleaved to yield two subunits of 53 and 341 amino acids, which remain noncovalently associated during secretion. The larger subunit is highly repetitive, containing 11 tandem repeats of a 19-amino acid sequence. Northern blot hybridization analysis showed a substantial increase in HSP150 mRNA level after heat shock. The upstream flanking region of the gene contains several heat shock element-like sequences. Disruption of HSP150 did not lead to inviability or significant effects on growth rate, mating, or thermotolerance. However, heat-regulated antigenic homologs of HSP150 were found in divergent yeasts such as Schizosaccharomyces pombe.

Amino Acid Sequence↗
PubMed1992

Expression of enzymatically active rat liver and human placental catechol-O-methyltransferase in Escherichia coli; purification and partial characterization of the enzyme.

To produce sufficient amounts of recombinant catechol-O-methyltransferase (COMT) for structural and functional studies the coding regions of the rat liver and human placental COMT genes have been introduced into a bacterial expression vector pKEX14. Recombinant COMT was produced in Escherichia coli up to 10% of total bacterial protein after the induction of the T7 RNA polymerase gene with isopropyl-beta-D-thiogalactopyranoside. Both the rat and human enzymes were enzymatically active, soluble and reacted with anti-COMT antiserum in Western blotting. Both enzymes were purified from E. coli cells and partially characterized by determining their specific activity, apparent molecular weight and pI.

Animals↗
PubMed1992

The two major xylanases from Trichoderma reesei: characterization of both enzymes and genes.

As a first step to exploit the potential of Trichoderma reesei to produce hemicellulases, we have purified two endo-beta-1,4-xylanases (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) and cloned their genes. The enzymes were isolated from culture filtrates of T. reesei C30 grown on xylan as a carbon source, using two steps of cation exchange chromatography. They exhibited molecular weights of 19 (XYN I) and 21 (XYN II) kD, and isoelectric points of 5.2 and 9.0, respectively. These enzymes differed in their pH optimum for activity and affinity for xylan, and accounted for more than 90% of the total xylanolytic activity of the fungus. The purified enzymes were subjected to N-terminal sequence analysis, and after cleavage with trypsin and endoproteinase Glu-C the resulting peptides were sequenced. Oligonucleotides based on these sequences were used to clone gene fragments via PCR, and these were used as probes to isolate full-length copies of xyn1 and xyn2 from a lambda gene bank of T. reesei. The products of xyn1 and xyn2 share considerable homology, but the enzyme encoded by xyn2 appears to more closely resemble several other bacterial and fungal xylanases than does that of xyn1.

Amino Acid Sequence↗
PubMed1991

Primary structure of bovine cathepsin S. Comparison to cathepsins L, H, B and papain.

The primary structure of bovine cathepsin S was determined by combining results of protein and peptide sequencing with the sequence deduced from nucleic acid sequencing. Using polymerase chain reaction (PCR) technology, cDNA clones commencing at amino acid 22 of the mature enzyme and continuing through the 3' untranslated region of bovine cathepsin S mRNA were isolated and sequenced. The open reading frame in these overlapping clones correctly predicts the determined amino acid sequence of 13 tryptic peptides derived from purified bovine spleen cathepsin S. The deduced amino acid sequence shows that mature bovine cathepsin S consists of 217 amino acids corresponding to a molecular weight of 23.7 kDa. Cathepsin S belongs to the papain superfamily of lysosomal cysteine proteinases and shares 41% identity with papain. Amino acid sequence identities of bovine cathepsin S to human cathepsins L, H, and B are 56%, 47% and 31% respectively.

Amino Acid Sequence↗
PubMed1991

Purification and partial sequence analysis of the soluble catechol-O-methyltransferase from human placenta: comparison to the rat liver enzyme.

Catechol-o-methyltransferase from human placenta was purified 1400-fold by hydroxyapatite adsorption, ammonium sulfate precipitation, gel filtration, high performance anion- exchange and reversed-phase chromatography. The purified enzyme has an apparent molecular weight of 26.000, an isoelectric point of 5,3 and is activated ten-fold in the presence of 20mM cysteine. The enzyme shows primary structure homology to the corresponding rat liver soluble enzyme, based on the sequenced tryptic peptides.

Amino Acid Sequence↗
PubMed1991

Genome organization of membrane-containing bacteriophage PRD1.

We have determined the nucleotide sequence of the late region (11 kbp) of the lipid-containing bacteriophage PRD1. Gene localization was carried out by complementing nonsense phage mutants with genomic clones containing specific reading frames. The localization was confirmed by sequencing the N-termini of isolated gene products as well as sequencing the N-termini of tryptic fragments of the phage membrane-associated proteins. This, with the previously obtained sequence of the early regions, allowed us to organize most of the phage genes in the phage genome.

Amino Acid Sequence↗
PubMed1991

Rapid production of interferon-gamma in uninduced human leukocyte suspensions.

Human leukocytes produced interferon-gamma (IFN-gamma) rapidly without induction during incubation at 37 degrees C. The intracellular level peaked at 3 h; the extracellular IFN-gamma reached its maximum at 7 h. Leukocytes purified by different methods, and whether from single donors or pooled from numerous donors, yielded similar amounts of IFN. The best yields were approximately 3 IU/10(6) cells. The highest titers were obtained at cell concentrations ranging between 30 and 100 X 10(6)/ml, and at these concentrations, the production of IFN-gamma was not affected by the presence or absence of serum. At lower cell concentrations, the yield of IFN per cell decreased markedly in the absence of serum. The cultural conditions and medium were not very critical; leukocytes incubated in various suspension and stationary cultures consistently produced IFN-gamma. We did not identify the mechanism responsible for the rapid production of IFN-gamma in vitro, but found no evidence of a role of calcium. Immunoaffinity-purified IFN-gamma from uninduced leukocytes and from leukocytes induced with lentil lectin behaved differently in gel filtration.

Cells, Cultured↗
PubMed1991

RGD-dependent entry of coxsackievirus A9 into host cells and its bypass after cleavage of VP1 protein by intestinal proteases.

The recently reported nucleotide sequence of coxsackievirus A9 (CAV-9) showed that unlike other enteroviruses, CAV-9 has an insertion of about 17 amino acids at the C-terminal end of VP1 (K. H. Chang, P. Auvinen, T. Hyypiä, and G. Stanway, J. Gen. Virol. 70:3269-3280, 1989). This sequence includes the RGD (arginine-glycine-aspartic acid) motif which is known to be important in certain protein-protein interactions. We studied the inhibitory effect of RGD-containing peptides in the attachment of CAV-9 to African green monkey kidney cells. A peptide corresponding to the RRGDM sequence derived from the inserted segment of CAV-9 was found to block virus attachment effectively, and the inhibition was dose dependent. Substitution of glutamic acid for the homologous aspartic acid completely abolished the inhibitory effect, indicating great specificity of the action. During replication in the gut, all enteroviruses are exposed to host proteolytic enzymes. Exposure of CAV-9 to purified trypsin or human intestinal fluid resulted in selective cleavage of the VP1 capsid protein. Intact and trypsin-cleaved VP1 proteins gave identical N-terminal sequences, indicating that cleavage of VP1 takes place near the C terminus. Attachment of proteolytically cleaved infectious CAV-9 to green monkey kidney cells was not prevented by RGD-containing peptides, indicating that cleaved CAV-9 is able to bypass RGD-dependent entry. The altered receptor specificity of proteolytically cleaved viruses may have important consequences in the pathogenesis of enteric infections.

Amino Acid Sequence↗
PubMed1990

Molecular cloning and characterization of rat liver catechol-O-methyltransferase.

The coding sequence of rat liver catechol-O-methyl-transferase (COMT; EC 2.1.1.6) was determined from rat cDNA and genomic libraries were screened with DNA probes and specific antiserum. The open reading frame consisted of 663 nucleotides coding for a 221-amino acid (aa) polypeptide with a deduced Mr of 24,747. No obvious hydrophobic signal sequence, membrane-spanning domains, or potential N-glycosylation sites were found in this sequence. The identity of the clone and the accuracy of the sequence was verified by direct aa sequencing of the tryptic peptides derived from the purified rat liver enzyme. Primer extension analysis showed that the transcription start point of the rat liver COMT mRNA was 450 bp upstream from the translation start codon. A putative polyadenylation signal (ATTAAA) was found in the 3'-noncoding region. The predicted size of the COMT transcript was 1.8-2.0 kb, which could be confirmed from Northern hybridization analyses of the isolated rat liver mRNA. One polypeptide of 25 kDa, could be immunoprecipitated with anti-COMT antibody from in vitro translation of rat liver mRNA. Employing the DNA blot analysis only one COMT-encoding gene was found in the rat genome.

Amino Acid Sequence↗
PubMed1990

Purification and partial characterization of rat liver soluble catechol-O-methyltransferase.

The rat liver soluble catechol-O-methyltransferase (EC 2.1.1.6.) has been purified utilizing a combination of conventional chromatography and HPLC. The purified enzyme has a molecular mass of 25 kDa, a pI of 5.1, and exists in two forms which differ in the nature of their intramolecular disulfide bonds. This difference causes these two protein forms to behave differently in reversed phase chromatography.

Amino Acid Sequence↗
PubMed1990

Comparison of two glucoamylases from Hormoconis resinae.

Two extracellular glucoamylases (EC 3.2.1.3), glucoamylase P and glucoamylase S, were purified to homogeneity from the culture medium of Hormoconis resinae (ATCC 20495; formerly Cladosporium resinae) by a new method. Their apparent molecular masses (71 kDa glucoamylase P; 78 kDa glucoamylase S) and catalytic properties agreed well with those previously reported in the literature. Heat inactivation studies suggested that the high debranching (1,6-glycosidic) activity of glucoamylase P preparations (measured with pullulan) may reside in the same protein molecule as its 1,4-glycosidic activity (measured with soluble starch). Although glucoamylase S had virtually no debranching activity, it cross-reacted with polyclonal antibodies raised against glucoamylase P, and the two enzymes had very similar amino acid compositions. However, peptide mapping and amino-terminal sequencing studies of the peptides showed that the two enzymes have different sequences and must be encoded by different genes.

Amino Acid Sequence↗