Suicide inactivation of bacterial cystathionine .gamma.-synthase and methionine .gamma.-lyase during processing of L-propargylglycine

Methionine gamma-lyase (EC 4.4.1.11) was purified to homogeneity from the anaerobic protozoan parasite Trichomonas vaginalis by a series of f.p.l.c. procedures. The enzyme catalyses alpha gamma- and alpha beta-elimination reactions of a number of derivatives of methionine and cysteine. It also catalyses gamma-replacement reactions of the thiomethyl group of methionine, homocysteine and ethionine to yield the corresponding S-substituted homocysteine derivative. The enzyme is pyridoxal 5′-phosphate-dependent, has a native molecular mass of approx. 160 kDa and consists of four apparently identical subunits of molecular mass 43-45 kDa. The absorption spectrum of the enzyme is typical of those obtained for other pyridoxal 5′-phosphate-dependent enzymes, and the holoenzyme can be resolved to the apoenzyme by incubation with hydroxylamine and reconstituted by addition of the cofactor. The enzyme activity is significantly affected by carbonyl and thiol reagents, is competitively inhibited by a number of substrate analogues and is completely inactivated by the suicide inhibitor DL-propargylglycine. The T. vaginalis enzyme is similar, in terms of activity and properties, to the enzymes found in a number of species of bacteria that metabolize methionine under anaerobic conditions. It is suggested that methionine catabolism may be of particular importance to the survival of T. vaginalis under microaerophilic conditions in its host.

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Suicide inactivation of xanthine oxidoreductase during reduction of inorganic nitrite to nitric oxide

Biochemical Journal ◽

10.1042/0264-6021:3580325 ◽

2001 ◽

Vol 358 (2) ◽

pp. 325 ◽

Cited By ~ 6

Author(s):

Ben L. J. GODBER ◽

Justin J. DOEL ◽

Tracey A. GOULT ◽

Robert EISENTHAL ◽

Roger HARRISON

Keyword(s):

Nitric Oxide ◽

Xanthine Oxidoreductase ◽

Suicide Inactivation

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Suicide inactivation of porcine leukocyte 12-lipoxygenase associated with its incorporation of 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid derivative

Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism ◽

10.1016/0005-2760(95)00241-3 ◽

1996 ◽

Vol 1300 (1) ◽

pp. 56-62 ◽

Cited By ~ 26

Author(s):

Koji Kishimoto ◽

Michihiro Nakamura ◽

Hiroshi Suzuki ◽

Tanihiro Yoshimoto ◽

Shozo Yamamoto ◽

...

Keyword(s):

Acid Derivative ◽

Eicosatetraenoic Acid ◽

Suicide Inactivation ◽

12 Lipoxygenase

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Suicide inactivation of aromatase in human placenta and uterine leiomyoma by 5α-dihydronorethindrone, a metabolite of norethindrone, and its effect on steroid-producing enzymes

Acta Endocrinologica ◽

10.1530/eje.0.1300634 ◽

1994 ◽

Vol 130 (6) ◽

pp. 634-640 ◽

Cited By ~ 5

Author(s):

Takara Yamamoto ◽

Takaya Tamura ◽

Jo Kitawaki ◽

Yoshio Osawa ◽

Hiroji Okada

Keyword(s):

Human Placenta ◽

Uterine Leiomyoma ◽

High Dose ◽

Aromatase Activity ◽

Dependent Manner ◽

Chain Cleavage ◽

Time Period ◽

Suicide Inactivation

Yamamoto T, Tamura T, Kitawaki J, Osawa Y, Okada H. Suicide inactivation of aromatase in human placenta and uterine leiomyoma by 5α-dihydronorethindrone, a metabolite of norethindrone, and its effect on steroid-producing enzymes. Eur J Endocrinol 1994;130:634–40. ISSN 0804–4643 Norethindrone (NET; 17α-ethynyl-19-nortestosterone), a progestogen component of the contraceptive pill, irreversibly inhibits aromatase activity in human placental microsomes. However, it is known also to be aromatized in vitro and in vivo to produce a biologically very active estrogen called ethynylestradiol (EE2). It is therefore inappropriate to administer a high dose of NET to estrogendependent cancer patients for a prolonged time period. In this study, we focused on 5α-dihydronorethindrone (5α-DHNET), a metabolite of NET that is not aromatizable, and the inhibitory effects of 5α-DHNET on human placental and uterine leiomyoma microsomal aromatase and other steroid synthetases. 5α-Dihydronorethindrone showed weak affinity for both estrogen and progestogen receptors. It inhibited significantly human placental aromatase activity in a dose-dependent manner (Ki = 9.0 μmol/l; Kinact = 0.024/min), as well as that of uterine leiomyoma, but did not influence cholesterol side-chain cleavage or 17α-hydroxylase, 21-hydroxylase or 11β-hydroxylase activities. These results suggest that 5α-DHNET may be useful as an aromatase inhibitor, whose use in large doses is expected to reduce the size of estrogen-dependent tumors. Takara Yamamoto, Department of Obstetrics and Gynecology, Kawaramachi-Hirokoji, Kamikyo-Ku, Kyoto 602, Japan

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