On The Kinetics of Human Erythrocyte Glutathione  Disulfide Reductase: Does The Enzyme Really Play  'Ping-Pong'?

Hamdi ÖĞÜŞ; Nazmi ÖZER

Makale detayları

On The Kinetics of Human Erythrocyte Glutathione Disulfide Reductase: Does The Enzyme Really Play 'Ping-Pong'?

Yazarlar:

Hamdi ÖĞÜŞ | Nazmi ÖZER

Yayıncı:

TUBITAK

Dergi:

Turkish Journal of Biology 1999 Vol.23 Issue 2, pp.143-152

Belge Tipi:

Makale

Yayın Tarihi:

1/1999

Belge Dili:

Türkçe

Document ID (Org No.):

2000814279

Sıklık:

İki Aylık

eISSN:

1303-6092

pISSN:

1300-0152

Anahtar kelimeler:

Özet:

 

: Human erythrocyte glutathione disulfide reductase studied at 37°C in 100 mM potassium  phosphate buffer, pH 7.4, is subject to partial inhibition by GSSG at low [NADPH]. Saturation by  NADPH is hyperbolic at low [GSSG] and becomes increasingly sigmoidal at high [GSSG]. NADP+ is a  competitive inhibitor with respect to NADPH at 20-1000 µM GSSG and an uncompetitive inhibitor  with respect to GSSG at 33-120 µM NADPH. Studied under special conditions (10 µM NADPH and  1000 µM GSSG), NADP+ exhibits a two-fold effect, inhibition being preceded by activation in the 0-  50 µM effector concentration range. The data are consistent with the ping-pong / sequential ordered  hybrid model diverging at the level of E.NADPH. A composite sequential ordered mechanism is  suggested, involving two conformational states of free enzyme at equilibrium. While one state is  selective for NADPH as the first substrate, the second state adds GSSG to initiate the catalytic cycle.  The pathway proceeding through E.GSSG has an apparently lower turnover number than that  proceeding through E.NADPH.

 

: Human erythrocyte glutathione disulfide reductase studied at 37°C in 100 mM potassium  phosphate buffer, pH 7.4, is subject to partial inhibition by GSSG at low [NADPH]. Saturation by  NADPH is hyperbolic at low [GSSG] and becomes increasingly sigmoidal at high [GSSG]. NADP+ is a  competitive inhibitor with respect to NADPH at 20-1000 µM GSSG and an uncompetitive inhibitor  with respect to GSSG at 33-120 µM NADPH. Studied under special conditions (10 µM NADPH and  1000 µM GSSG), NADP+ exhibits a two-fold effect, inhibition being preceded by activation in the 0-  50 µM effector concentration range. The data are consistent with the ping-pong / sequential ordered  hybrid model diverging at the level of E.NADPH. A composite sequential ordered mechanism is  suggested, involving two conformational states of free enzyme at equilibrium. While one state is  selective for NADPH as the first substrate, the second state adds GSSG to initiate the catalytic cycle.  The pathway proceeding through E.GSSG has an apparently lower turnover number than that  proceeding through E.NADPH.

Makale detayları

On The Kinetics of Human Erythrocyte Glutathione Disulfide Reductase: Does The Enzyme Really Play 'Ping-Pong'?

Yazarlar:

Hamdi ÖĞÜŞ | Nazmi ÖZER

Yayıncı:

TUBITAK

Dergi:

Turkish Journal of Biology 1999 Vol.23 Issue 2, pp.143-152

Belge Tipi:

Makale

Yayın Tarihi:

1/1999

Belge Dili:

Türkçe

Document ID (Org No.):

2000814279

Sıklık:

İki Aylık

eISSN:

1303-6092

pISSN:

1300-0152

Glutathione disulfide reductase

kinetics

mechanism

NADP+ inhibition

human erythrocytes.

Sayı

Makale detayları

On The Kinetics of Human Erythrocyte Glutathione Disulfide Reductase: Does The Enzyme Really Play 'Ping-Pong'?

Yazarlar: Hamdi ÖĞÜŞ | Nazmi ÖZER

Yayıncı: TUBITAK

Dergi: Turkish Journal of Biology 1999 Vol.23 Issue 2, pp.143-152

Belge Tipi: Makale

Yayın Tarihi: 1/1999

Belge Dili: Türkçe

Document ID (Org No.): 2000814279

Sıklık: İki Aylık

eISSN: 1303-6092

pISSN: 1300-0152

Glutathione disulfide reductase

kinetics

mechanism

NADP+ inhibition

human erythrocytes.

Sayı

Yazarlar:

Hamdi ÖĞÜŞ | Nazmi ÖZER

Yayıncı:

TUBITAK

Dergi:

Turkish Journal of Biology 1999 Vol.23 Issue 2, pp.143-152

Belge Tipi:

Makale

Yayın Tarihi:

1/1999

Belge Dili:

Türkçe

Document ID (Org No.):

2000814279

Sıklık:

İki Aylık

eISSN:

1303-6092

pISSN:

1300-0152