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E Fritsche

Publications and source records attributed to E Fritsche.

30 records · Page 2Linked to original sources
PubMed1997

Crystal structure and mechanism of human L-arginine:glycine amidinotransferase: a mitochondrial enzyme involved in creatine biosynthesis.

L-arginine:glycine amidinotransferase (AT) catalyses the committed step in creatine biosynthesis by formation of guanidinoacetic acid, the immediate precursor of creatine. We have determined the crystal structure of the recombinant human enzyme by multiple isomorphous replacement at 1.9 A resolution. A telluromethionine derivative was used in sequence assignment. The structure of AT reveals a new fold with 5-fold pseudosymmetry of circularly arranged betabeta alphabeta-modules. These enclose the active site compartment, which is accessible only through a narrow channel. The overall structure resembles a basket with handles that are formed from insertions into the betabeta alphabeta-modules. Binding of L-ornithine, a product inhibitor, reveals a marked induced-fit mechanism, with a loop at the active site entrance changing its conformation accompanied by a shift of an alpha-helix by -4 A. Binding of the arginine educt to the inactive mutant C407A shows a similar mode of binding. A reaction mechanism with a catalytic triad Cys-His-Asp is proposed on the basis of substrate and product bound states.

Amidinotransferases↗
PubMed1997

Recombinant expression and isolation of human L-arginine:glycine amidinotransferase and identification of its active-site cysteine residue.

Creatine and its phosphorylated form play a central role in the energy metabolism of muscle and nerve tissues. l-Arginine:glycine amidinotransferase (AT) catalyses the committed step in the formation of creatine. The mitochondrial and cytosolic forms of the enzyme are believed to derive from the same gene by alternative splicing. We have expressed recombinant human AT in Escherichia coli with two different N-termini, resembling the longest two forms of the enzyme that we had isolated recently from porcine kidney mitochondria as a mixture. The enzymes were expressed with N-terminal histidine tags followed by factor Xa-cleavage sites. We established a new method for the removal of N-terminal fusion peptides by means of an immobilized snake venom prothrombin activator. We identified cysteine-407 as the active-site residue of AT by radioactive labelling and isolation of labelled peptides, and by site-directed mutagenesis of the protein.

Amidinotransferases↗
PubMed1996

The inhibition of human immunodeficiency virus proteases by 'interface peptides'.

The active human immunodeficiency virus type 1 (HIV-1) protease has a homodimeric structure, the subunits are connected by an 'interface' beta-sheet formed by the NH2- and COOH-terminal amino acid segments. Short peptides derived from these segments are able to inhibit the protease activity in the range of micromolar IC50 values. We have further improved the inhibitory power of such peptides by computer modelling. The best inhibitor, the palmitoyl-blocked peptide Pam-Thr-Val-Ser-Tyr-Glu-Leu, has an IC50 value of less than 1 microM. Some of the peptides also showed very good inhibition of the HIV-2 protease. The C-terminal segment of the HIV-1 matrix protein, Acetyl-Gln-Val-Ser-Gln-Asn-Tyr, also inhibits HIV-1 protease. Kinetic studies confirmed the 'dissociative' mechanism of inhibition by the peptides. Depending on the peptide structure and ionic strength, both dimerization inhibition and competitive inhibition were observed, as well as synergistic effects between competitive inhibitors and interface peptides.

Antiviral Agents↗
PubMed1995

[Successful scalp replantation--a case report].

Scalp avulsion is a rare injury. Prior to the introduction of microsurgery, replantation usually resulted in partial or total necrosis. We present the case of a 19-year-old women with a severe scalp avulsion injury. The scalp was successfully replanted. For the relief of pressure to the replanted scalp we used a halo-fixateur externe.

Adult↗
PubMed1992

[Is follow-up of breast cancer with CEA and CA 15-3 justified?].

The significance of the tumor markers CEA and CA 15-3 for the oncological follow-up of breast cancer was examined in a retrospective analysis of 274 patients. Only 45% of 225 patients with nonmetastatic breast cancer showed in a period of 3 years normal values for both markers. 123 patients with increased markers in the same period were without evidence of tumor progression. Neither marker is suitable for the diagnosis of a local recurrence. In 32 cases of distant metastasis CA 15-3 is more sensitive than CEA (88%/63%), with an increase of 3% in sensitivity when analysing both markers simultaneously. The cut off level of CA 15-3 is problematic, 25 U/ml or 40 U/ml can be used as a threshold for tumoral activity. The use of tumor markers in the follow-up is not really justified so long as the prognosis or mortality of a patient is not changed by starting therapy early.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1991

Hypoglycemic symptoms and frequency of severe hypoglycemia in patients treated with human and animal insulin preparations.

OBJECTIVES: To compare hypoglycemic warning symptoms (main objective) and incidence of severe hypoglycemia (secondary objective) between patients treated with animal and human insulin preparations. RESEARCH DESIGN AND METHODS: Two hundred forty-seven patients on treatment with animal insulin preparations and 276 patients on human insulins, matched for duration of diabetes (16 +/- 11 vs. 15 +/- 10 yr), were recruited for the study. Patients were interviewed with a standardized questionnaire. RESULTS: When asked which symptom usually occurs first during hypoglycemia, 19% of the animal insulin group and 22% of the human insulin group answered "sweating," 19 and 17%, respectively, answered "trembling," and 15 and 11%, respectively, answered "unrest." According to the patients' perception, in both groups, their most reliable hypoglycemic warning symptoms were "trembling" (26 and 22%) and "sweating" (15 and 18%). Six and eight percent of patients, respectively, reported hypoglycemia unawareness and 17 and 18%, respectively, impaired awareness of hypoglycemia. The incidence of severe hypoglycemia was 0.45 cases/patient-yr in patients treated with animal insulins and 0.46 cases/patient-yr in patients treated with human insulin preparations. The differences were not statistically significant. CONCLUSIONS: This study shows that hypoglycemic warning symptoms and the incidence of severe hypoglycemia are comparable between patients on treatment with human and animal insulin preparations.

Adult↗
PubMed1991

[Direction-dividing road construction measures and their consequences in traffic. An analysis of 1120 accident protocols prior to and following opening of a freeway section].

We analysed the traffic accidents on a typical Swiss road traffic about 14 km and over a period of 11 years before and after the building of a motorway. A new rotat is the most important factor for a really current number of traffic accidents. In the same time we registered a higher density flow of traffic on these roads.

Accidents, Traffic↗
PubMed1989

[Suture of the Achilles tendon with a reinforcing-plasty--experiences with 30 primary sutures of Achilles tendon ruptures].

We analysed 32 patients with fresh Achilles tendon rupture. 30 operations with a special primary suture and plasty of the fascia triceps muscle. Most of the patients were content with the operative treatment and the functional result. We saw one wound infection and one wound rand necrosis. The objective controls of OSG foot function and the muscle activity is good.

Achilles Tendon↗
PubMed1981

[The synthesis, analysis, stability and biotransformation of N-(3-methylphenyl)-N'-cyanobenzamidine and analogues (author's transl)].

The antivirally active N-(3-methylphenyl)-N'-cyanobenzamidine (1) and some of its analogues were synthetized by the reaction of the ethyl ester of N-cyanobenzimidic acid with the corresponding arylamines. The analytical profile of 1 and of some of its analogues, which is needed for stability and biotransformation studies, was established by means of the following techniques: solubility determination, TLC, UV, IR and MS. When 1 is heated with methanolic HCl and NaOH (0.5 mol/l) for 1 h, several hydrolysis products are formed: m-toluidine, benzoic acid, benzoic acid 3-toluidide, N-(3-methylphenyl)benzamidine, N-(3-methylphenyl)-N'-carboxamidobenzamidine, benzoylurea, However, 1 is fairly stable under physiological conditions so biotransformation studies are not affected. After oral application of 1 to rats, the 3-hydroxymethyl and the 3-methyl-5-hydroxy compound as well as its glucuronide and sulphate conjugate were detected in the urine. The faeces contained considerable amounts of unchanged 1 (incomplete absorption).

Amidines↗
PubMedDate not supplied

Increased frequencies of cytochrome P4501A1 polymorphisms in infertile men.

Genetic factors that could mediate the pathogenesis of male reproductive disorders are largely unclear. Polymorphisms of cytochrome P4501A1 (CYP1A1), a key enzyme in the extrahepatic metabolism of lipophilic xenobiotics, have been shown to influence susceptibility to xenobiotics. Here, CYP1A1 polymorphisms were investigated in 134 infertile Caucasian men. The frequencies of the Mspl polymorphism in the 3'-flanking region of the CYP1A1 gene and a mutation in exon 7 causing an isoleucine-valine exchange (IVE) in the heme-binding region of the enzyme were increased among infertile men when compared with those of unselected, healthy male controls (odds ratio (OR)) 1.4, Cl95 0.68-2.89 for Mspl polymorphism; OR 2.4, Cl95 0.83-6.95 for IVE). Patients with normozoospermia revealed the highest frequencies for both polymorphisms (n = 8; OR 4.5, Cl95 0.97-20.91 for Mspl polymorphism; OR 13.7, Cl95 2.53-74.13 for IVE). ORs for the IVE exceeded the values calculated for the Mspl polymorphism. These preliminary results suggest that genetic variation in the metabolism of xenobiotics may codetermine individual susceptibility to infertility.

Cytochrome P-450 CYP1A1↗
PubMedDate not supplied

Structure and reaction mechanism of L-arginine:glycine amidinotransferase.

L-Arginine:glycine amidinotransferase (AT) catalyzes the committed step in creatine biosynthesis by formation of guanidinoacetic acid, the direct precursor of creatine. The X-ray structure of the human enzyme shows a novel fold with fivefold pseudosymmetry of beta beta alphabeta-modules. These modules enclose the active site compartment of the basket-like structure. The active site of AT lies at the bottom of a very narrow channel and contains a catalytic triad with the residues Cys-His-Asp. The transamidination reaction follows a ping-pong mechanism and is accompanied by large conformational changes. During catalysis the amidino group is covalently attached to the active site cysteine to give an amidino-cysteine intermediate.

Amidinotransferases↗