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8.A.7 The Phosphotransferase System Enzyme I (EI) Family

Enzymes I (EC# 2.A.7.9.3) of the phosphotransferase system (PTS) serve as energy coupling proteins for PTS porters. Phosphoenolpyruvate (PEP) is the energy source and phosphoryl donor. PEP phosphorylates a histidyl residue in EI; this is then passed to a histidyl residue in a heat stable phopho-carrier protein called HPr, and the phosphoryl group is then transferred to a histidyl residue in the IIA domain/protein of a PTS porter (TC #4.A.1-4.A.7) (Brackenbury and Isom, 2011).

Enzymes I are homologous to PEP synthases (EC# and pyruvate:orthophosphate dikinases (EC Five Enzyme I paralogues are encoded within the genome of E. coli. The functions of several of these proteins are not known, but they probably function in PTS-related transport, phosophorylation or regulatory capacities.

References associated with 8.A.7 family:

Araki N., Suzuki T., Miyauchi K., Kasai D., Masai E. and Fukuda M. (201). Identification and characterization of uptake systems for glucose and fructose in Rhodococcus jostii RHA1. J Mol Microbiol Biotechnol. 20(3):125-36. 21464575
Brackenbury, W.J. and L.L. Isom. (2011). Na Channel β Subunits: Overachievers of the Ion Channel Family. Front Pharmacol 2: 53. 22007171
Pickl A., Johnsen U. and Schonheit P. (2012). Fructose degradation in the haloarchaeon Haloferax volcanii involves a bacterial type phosphoenolpyruvate-dependent phosphotransferase system, fructose-1-phosphate kinase, and class II fructose-1,6-bisphosphate aldolase. J Bacteriol. 194(12):3088-97. 22493022
Postma, P.W., J.W. Lengeler and G.R. Jacobson (1993). Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria. Microbiol. Rev. 57: 543-594. 8246840
Reizer, J., C. Hoischen, A. Reizer, T.N. Pham and M.H. Saier, Jr. (1993). Sequence analyses and evolutionary relationships among the energy-coupling proteins Enzyme I and HPr of the bacterial phosphoenolpyruvate:sugar phosphotransferase system. Prot. Sci. 2: 506-521. 7686067