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R J Cook

Publications and source records attributed to R J Cook.

At least 163 records · Page 9Linked to original sources
PubMed1984

Identification of the covalently bound flavin of dimethylglycine dehydrogenase and sarcosine dehydrogenase from rat liver mitochondria.

Dimethylglycine dehydrogenase (EC 1.5.99.2) and sarcosine dehydrogenase (EC 1.5.99.1) are the folate binding proteins of rat liver mitochondria. These two enzymes contain covalently bound flavin and catalyze similar oxidative demethylation reactions (Wittwer, A. J., and Wagner, C. (1981) J. Biol. Chem. 256, 4102-4108). Flavin-peptides have been purified from these two enzymes after proteolytic digestion by trypsin and chymotrypsin. The spectral and chromatographic properties of these flavin peptides changed after treatment with nucleotide pyrophosphatase in a manner consistent with the conversion of an FAD-peptide to an FMN-peptide. The pKa for pH-dependent fluorescence quenching of the purified flavin-peptides was not affected by borohydride reduction which, in conjunction with the pKa values, indicated that the flavin was covalently linked via the 8 alpha position of the isoalloxazine ring to an imidazole N(3) of a histidine residue. Peptides from both enzymes showed histidylflavin at the N terminus. Amino acid composition and sequence analysis showed that the flavin-peptide from dimethylglycine dehydrogenase was His(flavin)-Ala-Ala-Gly-Leu. Amino acid composition and N-terminal analysis suggested the sequence of the flavin-peptide of sarcosine dehydrogenase was His(flavin)-(Ala, Gly,Thr)-Leu.

Amino Acids↗
PubMed1984

Covalent binding of folic acid to dimethylglycine dehydrogenase.

Dimethylglycine dehydrogenase (EC 1.5.99.2) carries out the oxidative demethylation of dimethylglycine to sarcosine in liver mitochondria. In vivo, the enzyme uses tightly bound tetrahydropteroyl pentaglutamate (H4PteGlu5) as an acceptor of the one-carbon group generated during the reaction. The purified enzyme can use, but does not require, H4PteGlu5 and under these conditions formaldehyde is the one-carbon unit produced. It is reported that folic acid may be covalently linked to dimethylglycine dehydrogenase in a specific and saturable manner so that only 1 mole of folic acid is bound per mole of enzyme. Covalently bound folic acid blocks the subsequent binding of H4PteGlu, and does not inhibit the rate of dimethylglycine dehydrogenase activity in vitro.

Animals↗
PubMed1984

Glycine N-methyltransferase is a folate binding protein of rat liver cytosol.

A comparison of the amino acid compositions of one of the folate-binding proteins of rat liver cytosol, folate-binding protein-cytosol II, and that of glycine N-methyltransferase (S-adenosyl-L-methionine:glycine methyltransferase, EC 2.1.1.20) from the same source indicated a great deal of structural homology between the two proteins. Antiserum prepared against the purified folate-binding protein almost completely inactivated the enzyme activity in crude liver cytosol. Purification of glycine N-methyltransferase resulted in the separation of two enzyme species, one that contained bound folate and one that did not. Each species was homogeneous, as judged by NaDodSO4/polyacrylamide gel electrophoresis, and they migrated identically.

Amino Acids↗
PubMed1982

Purification and partial characterization of rat liver folate binding protein: cytosol I.

The high molecular weight folate binding protein of rat liver cytosol has been purified to apparent homogeneity. Purification was achieved by using a combination of gel filtration, O-(diethylaminoethyl)cellulose chromatography, and affinity chromatography. This folate binding protein was initially identified during purification by an in vivo labeling procedure involving intraperitoneal injection of [3H]folic acid prior to sacrifice and subsequently by its ability to bind naturally reduced [3H]folate polyglutamates in vitro. A molecular weight of 210 000 was estimated by gel chromatography. This is distinct from the trifunctional formyl-methenyl-methylene synthetase of rat liver which has a molecular weight of 225 000. Sodium dodecyl sulfate electrophoresis revealed a single band with a molecular weight of about 100 000 which suggests the native protein is composed of two identical subunits. The partially purified protein contains bound tetrahydropteroylpentaglutamate.

Animals↗
PubMed1979

The distribution and chemical nature of radioactive folates in rat liver cells and rat liver mitochondria.

Subcellular fractionation of rat liver cells revealed that a mixture of 14C- and 3H-labelled folic acid was distributed approximately equally between the mitochondria and cytosol 2, 24, 48 and 72 h after oral administration. Subfractionation of liver mitochondria 48 h after oral administration showed that the radioactivity was mainly associated with the inner membrane (27.7%) and matrix (51.5%). Hot-ascorbate extraction of the cell cytosol, mitochondrial inner membrane and matrix showed the majority of folates were present as polyglutamates. Acid treatment of isolated folates from cytosol, inner membrane and matrix produced breakdown products consistent with scission of tetrahydrofolates. The folates isolated in the mitochondrial matrix were bound to protein that had an estimated mol. wt. of 90,000.

Animals↗
PubMed1978

A decade of international change in abortion law: 1967-1977.

Modern thinking on abortion, reflected in recent legal developments around the world, has turned from concentration upon criminality in favor of female and family well-being. New laws enacted during the last decade are coming to focus upon conditions of health and social welfare of women and their existing families as indications for lawful termination of pregnancy. Regulations governing the delivery of services may be restrictive, however, so as to limit in practice access to means of safe, legal abortion made available in theory. Requirements may be imposed that only medical personnel with unduly high qualifications perform procedures, or that they be undertaken only in institutions meeting standards higher than similar health care requires. Approval procedures may be established involving second medical opinions or committees to monitor observance of the law, which may delay abortions and therefore increase their hazards. Parental and spousal consent requirements may exist in addition with the same effects, or to veto a pregnant female's request. Regulations may be employed more positively, however, to encourage contraceptive practice. A disappointment with legislative reform is that it may fail to improve circumstances if public resources are not applied to achieve the supply of services newly rendered legitimate, and illegal practice may persist.

Abortion, Legal↗