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New vistas for P-aminobenzoate participation in the biosynthesis of dihydro folate: a tentative model of the tetrahydro folate multienzyme complex.
Authors:B L Tóth-Martinez  S Papp  Z Dinya  F J Hernádi
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
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.
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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