Carbamoyl-phosphate synthetase II of the mammalian CAD protein: kinetic mechanism and elucidation of reaction intermediates by positional isotope exchange

Biochemistry ◽  
1987 ◽  
Vol 26 (9) ◽  
pp. 2584-2593 ◽  
Author(s):  
Thomas D. Meek ◽  
William E. Karsten ◽  
Charles W. DeBrosse
Keyword(s):  
Isotope Exchange ◽  
Kinetic Mechanism ◽  
Reaction Intermediates ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Cad Protein

Kinetic mechanism of Escherichia coli carbamoyl-phosphate synthetase

Biochemistry ◽  
1978 ◽  
Vol 17 (26) ◽  
pp. 5587-5591 ◽  
Author(s):  
Frank M. Raushel ◽  
Paul M. Anderson ◽  
Joseph J. Villafranca
Keyword(s):  
Escherichia Coli ◽  
Kinetic Mechanism ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate

scholarly journals Substitutions in hamster CAD carbamoyl-phosphate synthetase alter allosteric response to 5-phosphoribosyl-alpha-pyrophosphate (PRPP) and UTP

2004 ◽  
Vol 378 (3) ◽  
pp. 991-998 ◽  
Author(s):  
Christine Q. SIMMONS ◽  
Alan J. SIMMONS ◽  
Aaron HAUBNER ◽  
Amber REAM ◽  
Jeffrey N. DAVIDSON
Keyword(s):  
De Novo ◽  
Binding Pocket ◽  
Tryptophan Residue ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Aspartate Transcarbamylase ◽  
Inosine Monophosphate ◽  
E Coli ◽  
Mammalian Enzyme ◽  
Cad Protein

CPSase (carbamoyl-phosphate synthetase II), a component of CAD protein (multienzymic protein with CPSase, aspartate transcarbamylase and dihydro-orotase activities), catalyses the regulated steps in the de novo synthesis of pyrimidines. Unlike the orthologous Escherichia coli enzyme that is regulated by UMP, inosine monophosphate and ornithine, the mammalian CPSase is allosterically inhibited by UTP, and activated by PRPP (5-phosphoribosyl-α-pyrophosphate) and phosphorylation. Four residues (Thr974, Lys993, Lys954 and Thr977) are critical to the E. coli inosine monophosphate/UMP-binding pocket. In the present study, three of the corresponding residues in the hamster CPSase were altered to determine if they affect either PRPP activation or UTP inhibition. Substitution of the hamster residue, positionally equivalent to Thr974 in the E. coli enzyme, with alanine residue led to an enzyme with 5-fold lower activity and a near loss of PRPP activation. Whereas replacement of the tryptophan residue at position 993 had no effect, an Asp992→Asn substitution yielded a much-activated enzyme that behaved as if PRPP was present. The substitution Lys954→Glu had no effect on PRPP stimulation. Only modest decreases in UTP inhibitions were observed with each of the altered CPSases. The results also show that while PRPP and UTP can act simultaneously, PRPP activation is dominant. Apparently, UTP and PRPP have distinctly different associations within the mammalian enzyme. The findings of the present study may prove relevant to the neuropathology of Lesch–Nyhan syndrome.

scholarly journals Kinetic studies of bovine liver carbamoyl phosphate synthetase

1974 ◽  
Vol 141 (3) ◽  
pp. 807-816 ◽  
Author(s):  
Keith R. F. Elliott ◽  
Keith F. Tipton
Keyword(s):  
Initial Rate ◽  
Kinetic Studies ◽  
Bovine Liver ◽  
Kinetic Mechanism ◽  
Rate Equations ◽  
British Library ◽  
Rate Data ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Lending Library

A through study of initial-rate data has been made on carbamoyl phosphate synthetase from bovine liver. On the basis of the results the order of substrate binding to the enzyme is ATPMg followed by HCO3−, ATPMg and NH4+. A model for the enzymic mechanism is proposed, and the rate equations describing it are presented. Details of the derivation of the initial-rate equation for the kinetic mechanism proposed have been deposited as Supplementary Publication SUP 50032 (6 pages) at the British Library, Lending Division (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7QB, U.K., from whom copies may be obtained on the terms indicated in Biochem. J. (1973), 131, 5.

scholarly journals Product inhibition studies on bovine liver carbamoyl phosphate synthetase

1974 ◽  
Vol 141 (3) ◽  
pp. 817-824 ◽  
Author(s):  
Keith R. F. Elliott ◽  
Keith F. Tipton
Keyword(s):  
Inorganic Phosphate ◽  
Substrate Binding ◽  
Inorganic Ions ◽  
Bovine Liver ◽  
Product Inhibition ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Product Release ◽  
Proposed Model ◽  
Inhibition Studies

A study of the product-inhibition patterns of carbamoyl phosphate synthetase from bovine liver is reported. Inhibition by adenosine, AMP and inorganic ions is also reported. The results are in agreement with the previously proposed model in which the order of substrate binding is ATPMg, followed by HCO3−, ATPMg and NH4+. The order of product release on the basis of the reported results is carbamoyl phosphate, followed by ADPMg, ADPMg and inorganic phosphate.

Inactivation by acivicin of carbamoyl-phosphate synthetase II of human colon carcinoma

1985 ◽  
Vol 34 (1) ◽  
pp. 97-100 ◽  
Author(s):  
Judith S. Sebolt ◽  
Takashi Aoki ◽  
John N. Eble ◽  
John L Glover ◽  
George Weber
Keyword(s):  
Colon Carcinoma ◽  
Human Colon ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Human Colon Carcinoma
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