New vistas for P-aminobenzoate participation in the biosynthesis of dihydro folate: a tentative model of the tetrahydro folate multienzyme complex. |
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Authors: | B L Tóth-Martinez S Papp Z Dinya F J Hernádi |
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Affiliation: | 1. Institute of Pharmacology, Debrecen Medical University, Kossuth Lajos University of Sciences, Debrecen, Hungary;2. Department of Organic Chemistry, Kossuth Lajos University of Sciences, Debrecen, Hungary |
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Abstract: | Figures 6a and 6b and Table 2 show the united pattern of possible pathways of THFA biosynthesis with the substrates and the enzymes involved. With substrate selection ten different individual enzyme activities can be distinguished, but A2′ is identical with A2, and their apparent molecular weight is 28,000 daltons ±7%, and similarly c1–4 are the same enzymes with an apparent molecular weight of 40,000 daltons ±5% (Tóth-Martinez et al., 1974a). The identity of these enzymes has preliminary been shown, and construction of the THFA-MEC model was partly based on these findings.So, no distinction can be made among functioning MEC-es. The different pathways, mentioned in the introductory part of this paper, can be a product of the separated study of the individual enzymic steps of DHFA (THFA) biosynthesis. By all means it is an important approach to understand the dynamics of the integrated process what we tentatively suggest in this paper for further elucidation. |
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Keywords: | Pter 7,8-dihydro-6-hydroxymethyl pteridine PterPP 7,8-dihydro-6-hydroxymethyl pteridine pyrophosphate pABA p-amino benzoic acid pABApup p-aminobenzoate pick up protein pABGA p-aminobenzoyl glutamic acid pABGAS p-aminobenzoyl glutamate synthetase L-GluA L-glutamic acid DHPA 7,8-dihydro pteroic acid DHPAS 7,8-dihydropteroate synthetase DHPK 7,8-dihydro-6-hydroxymethyl pteridine ATP pyrophosphokinase DHFA 7,8-dihydro folic acid DHFAS I and -II 7,8-dihydrofolate synthetase I and -II DHFR 7,8-dihydrofolate reductase (5,6,7,8-tetrahydrofolate NADP oxidoreductase, E.C. 1.5.1.3.) THFA 5,6,7,8-tetrahydro folic acid ATP adenosine triphosphoric acid GTP guanosine triphosphoric acid SA sulfonamide TMP trimethoprim (2,6-diamino-5-) 3′,4′,5′-trimethoxybenzyl(-pyrimidine) GHCl guanidine hydrochloride EDTA ethylendiamine tetra acetic acid |
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