Homocystinuria due to cystathionine synthase deficiency. Studies of nitrogen balance and sulfur excretion.

Poole, Jeffery R.; Mudd, S. Harvey; Conerly, E B; Edwards, William

doi:10.1172/jci108004

Cited by 29 publications

(7 citation statements)

References 43 publications

(65 reference statements)

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“…Cystine was measured with a cystinebinding protein assay (8). Urinary sulfur and sulfate were determined as previously described (14). Urinary and plasma amino acids were determined with a Durrum 500 amino acid analyzer (Durrum Instrument Corp., Palo Alto, Calif.) (15).…”

Section: Methodsmentioning

confidence: 99%

Cystinosis. Intracellular cystine depletion by aminothiols in vitro and in vivo.

Thoene¹,

Oshima²,

Crawhall³

et al. 1976

J. Clin. Invest.

316

164

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Section: Methodsmentioning

confidence: 99%

Cystinosis. Intracellular cystine depletion by aminothiols in vitro and in vivo.

Thoene¹,

Oshima²,

Crawhall³

et al. 1976

J. Clin. Invest.

316

164

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“…In the steady-state metabolic condition in normal individuals, the intake of Met sulfur is balanced by metabolism of an almost equivalent amount of Hcy sulfur through the transsulfuration pathway (Mudd et al 1980; Poole et al 1975; Stipanuk 1986; Storch et al 1988). This must be true regardless of the extent of remethylation.…”

Section: Transsulfuration Is Necessary For Homocysteine/methionine Sumentioning

confidence: 99%

Dealing with methionine/homocysteine sulfur: cysteine metabolism to taurine and inorganic sulfur

Stipanuk

Ueki

2010

J of Inher Metab Disea

403

294

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Synthesis of cysteine as a product of the transsulfuration pathway can be viewed as part of methionine or homocysteine degradation, with cysteine being the vehicle for sulfur conversion to end products (sulfate, taurine) that can be excreted in the urine. Transsulfuration is regulated by stimulation of cystathionine β-synthase and inhibition of methylene tetrahydrofolate reductase in response to changes in the level of S-adenosylmethionine, and this promotes homocysteine degradation when methionine availability is high. Cysteine is catabolized by several desulfuration reactions that release sulfur in a reduced oxidation state, generating sulfane sulfur or hydrogen sulfide (H2S), which can be further oxidized to sulfate. Cysteine desulfuration is accomplished by alternate reactions catalyzed by cystathionine β-synthase and cystathionine γ-lyase. Cysteine is also catabolized by pathways that require the initial oxidation of the cysteine thiol by cysteine dioxygenase to form cysteinesulfinate. The oxidative pathway leads to production of taurine and sulfate in a ratio of approximately 2:1. Relative metabolism of cysteine by desulfuration versus oxidative pathways is influenced by cysteine dioxygenase activity, which is low in animals fed low-protein diets and high in animals fed excess sulfur amino acids. Thus, desulfuration reactions dominate when cysteine is deficient, whereas oxidative catabolism dominates when cysteine is in excess. In rats consuming a diet with an adequate level of sulfur amino acids, about two thirds of cysteine catabolism occurs by oxidative pathways and one third by desulfuration pathways. Cysteine dioxygenase is robustly regulated in response to cysteine availability and may function to provide a pathway to siphon cysteine to less toxic metabolites than those produced by cysteine desulfuration reactions.

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“…Evidently, even in this patient where the transaminative pathway will be favoured, the pathway cannot 'handle' excess methionine and methionine accumulates [9]. Gahl et al also pointed out that patients with cystathionine synthase (EC 4.2.1.22) deficiency are grossly defective in their maximum capacity to convert methionine sulphur to sulphate (see [10,11]). Furthermore, in a hypermethionaemic patient in whom the concentration of urinary 2-oxo-4-methylthiobutyrate was monitored, the daily output of this 2-oxo acid was negligible [10].…”

Section: Methionine Transamination In Vivomentioning

confidence: 99%

Methionine transamination in vivo

Cooper¹

1989

Biochemical Journal

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Homocystinuria due to cystathionine synthase deficiency. Studies of nitrogen balance and sulfur excretion.

Cited by 29 publications

References 43 publications

Cystinosis. Intracellular cystine depletion by aminothiols in vitro and in vivo.

Cystinosis. Intracellular cystine depletion by aminothiols in vitro and in vivo.

Dealing with methionine/homocysteine sulfur: cysteine metabolism to taurine and inorganic sulfur

Methionine transamination in vivo

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