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Biomedical subjects

H Follmann

Publications and source records attributed to H Follmann.

61 records · Page 4Linked to original sources
PubMedDate not supplied

Multiple functions of thioredoxins.

Reduced thioredoxins from microbial and plant cells, both of cytoplasmic or chloroplast origin, are interchangeable in stimulating such diverse enzyme activities as ribonucleoside diphosphate reductase (E. coli), PAPS sulfotransferase (Synechococcus), and fructose-1,6-bis-phosphatase (from spinach) in vitro. It is suggested that reduced thioredoxins are unspecific, multifunctional cellular proteins while in contrast the oxidized froms require specific enzymes for their reduction.

Bacterial Proteins↗
PubMedDate not supplied

A study of the substrate and inhibitor specificities of AMP aminohydrolase, 5'-nucleotidase, and adenylate kinase with adenosine carboxylates of variable chain length.

A series of AMP analogs in which a terminal carboxylate residue, linked to C 4' of the ribose moiety of adenosine by zero, one, or two methylene groups (1,2,3) or by the unsaturated ethylidene link (4) replaces the phosphate anion, is tested for activity as substrates or effectors of three enzymes known to interact with AMP with a different degree of specificity. 2-4 are substrates of AMP aminohydrolase, 3 and 4 are competitive inhibitors of adenylate kinase, and all acids produce competitive inhibition of the least specific enzyme, 5'-nucleotidase. These activities can be correlated with the intramolecular flexibility of anionic substituent and adenine base which in turn is expressed in typical shifts of the proton magnetic resonance signal of purine H-8. The uronic acid 1, having a rigid molecular conformation, is inactive towards two AMP-dependent enzymes and little active with the third, indicating that this type of compound is not suitable as a nucleotide antagonist whereas nucleoside carboxylates of type 2 and 3 have a higher potential as effectors of nucleotide metabolism.

5'-Nucleotidase↗
PubMedDate not supplied

Irregularities in the circular dichroism of oligoribonucleotides.

Marked anomalies, previously unresolved, exist in the CD spectra of oligoadenylates and oligouridylates at the pentamer or tetramer stage, indicating that these molecules differ in conformation from the preceding and the following member of the series. The CD of oligoadenylates retains a positive Cotton effect even at 80 degrees C. Caution must be exerted when predicting oligonucleotide structures from CD spectra.

Adenine Nucleotides↗
PubMedDate not supplied

Aurintricarboxylic acid and polynucleotides as novel inhibitors of ribonucleotide reductases.

Ribonucleoside diphosphate reductases isolated from Escherichia coli, baker's yeast, Ehrlich ascites tumor cells, and unicellular green alga (Scenedesmus obliquus) are inhibited strongly and uniformly by the polymeric triphenylmethane dye, aurintricarboxylic acid. The molecule appears to interact simultaneously with the enzyme's various nucleotide and catalytic (iron-organic radical) sites. Oligo- and polyribonucleotides are also inhibitory. These reactions serve as models of the probably physiologic regulation of ribonucleotide reduction exerted by natural inhibitors. Partial characterization of an inhibitor fraction found in wheat seed embryo is described.

Animals↗
PubMedDate not supplied

Deoxyribonucleotide synthesis in an Escherichia coli mutant (H 1491) which lacks ribonucleotide reductase subunit B2.

An iron-sensitive mutant of E. coli with a Mudl phage insertion in the nrdB gene lacks subunit B2 of the key enzyme of DNA synthesis, ribonucleotide reductase. Nevertheless, these cells are capable of growing in minimal media under anaerobic conditions, indicating a second enzyme or pathway for deoxyribonucleotide synthesis. We here show that ribonucleotide reduction cannot be unambiguously measured in bacterial extracts whereas phosphorylase-catalyzed deoxyribosyl transfer does occur; however these salvage reactions could not function in vivo in the absence of deoxyribosides. It is suggested that the cells possess a specific, anaerobic ribonucleotide reductase which escapes detection under aerobic standard conditions, similar to the situation found in strictly anaerobic methanogens.

Anaerobiosis↗
PubMedDate not supplied

Characterization of two thioredoxins in pig heart including a new mitochondrial protein.

Heart tissue contains two different thioredoxins. One is a specific mitochondrial protein and is best prepared from pre-isolated, intact heart mitochondria (mt-thioredoxin) whereas mitochondria-depleted tissue homogenates contain the major cellular thioredoxin of cytoplasmic origin (c-thioredoxin). Both heat-stable proteins are clearly differentiated chromatographically. They exhibit slightly different molecular weights (12,300 vs. 12,000) and isoelectric points (4.7 vs. 4.8) but differ remarkably in their cysteine content: mt-Thioredoxin has two cysteine residues like the bacterial proteins, and c-thioredoxin possesses six cysteines. Heart extracts were also shown to contain a NADPH-specific thioredoxin reductase of the known mammalian type. A specific function or target enzyme of mt-thioredoxin has not as yet been established.

Amino Acids↗