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Titolo:
Preparation and properties of a selenium-containing catalytic antibody as type I deiodinase mimic
Autore:
Lian, GW; Ding, L; Chen, M; Liu, Z; Zhao, DQ; Ni, JZ;
Indirizzi:
Changchun Univ Agr & Anim Husb Sci, Inst Mil Vet Sci, Changchun 130021, Peoples R China Changchun Univ Agr & Anim Husb Sci Changchun Peoples R China 130021 hina Chinese Acad Sci, Changchun Inst Appl Chem, Lab Rare Earth Chem & Phys, Changchun 130022, Peoples R China Chinese Acad Sci Changchun Peoples R China 130022 30022, Peoples R China
Titolo Testata:
JOURNAL OF BIOLOGICAL CHEMISTRY
fascicolo: 30, volume: 276, anno: 2001,
pagine: 28037 - 28041
SICI:
0021-9258(20010727)276:30<28037:PAPOAS>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
RAT-LIVER; IODOTHYRONINE DEIODINASE; PARTIAL-PURIFICATION; 5'-DEIODINASE; MICROSOMES; THYROXINE; ENZYME; KIDNEY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
28
Recensione:
Indirizzi per estratti:
Indirizzo: Ding, L Chinese Acad Sci, Changchun Inst Appl Chem, Lab Rare Earth Chem & Phys, Changchun 130022, Peoples R China Chinese Acad Sci Changchun Peoples R China 130022 eoples R China
Citazione:
G.W. Lian et al., "Preparation and properties of a selenium-containing catalytic antibody as type I deiodinase mimic", J BIOL CHEM, 276(30), 2001, pp. 28037-28041

Abstract

Conversion of thyroxine (T-4) to 3,5,3'-triiodothyronine is an essential first step in controlling thyroid hormone action. Type I deiodinase (DI) cancatalyze the conversion to produce the bulk of serum 3,5,3'-triiodothyronine. Acting as a mimic of DI, a selenium-containing catalytic antibody (Se-4C5) prepared by converting the serine residues of monoclonal antibody 4C5 raised against T4 into selenocysteines, can catalyze the deiodination of T4 with dithiothreitol (DTT) as cosubstrate. The mimic enzyme Se-4C5 exhibiteda much greater deiodinase activity than model compound ebselen and anotherselenium-containing antibody Se-Hp4 against GSH. The coupling of selenocysteine with the combining pocket of antibody 4C5 endowed Se-4C5 with enzymatic activity. To probe the catalytic mechanism of the catalytic antibody, detailed kinetic studies were carried out in this paper. Investigations into the deiodinative reaction revealed the relationship between the initial velocity and substrate concentration. The characteristic parallel Dalziel plots demonstrated that Se-4C5-catalyzed reaction mechanism was ping-pong one, involving at least one covalent enzyme intermediate. The kinetic propertiesof the catalytic antibody were similar to those of DI, with K-m values forT-4 and DTT of approximately 0.8 muM and 1.8 muM, respectively, and a V-m value of 270 pmol per mg of protein per min. The activity could be sensitively inhibited by 6-propyl-2-thiouracil (PTU) with a K-i value of similar to120 muM at 2.0 muM T-4 concentration. The PTU inhibition was progressivelyalleviated with the increasing concentration of added DTT, revealing that PTU was a competitive inhibitor for DTT.

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Documento generato il 25/11/20 alle ore 17:40:53