Vorobyeva NN, Kurilova SA, Vlasova AV, Anashkin VA, Nazarova TI, Rodina EV, Baykov AA. Constitutive inorganic pyrophosphatase as a reciprocal regulator of three inducible enzymes in Escherichia coli.
Biochim Biophys Acta Gen Subj 2020;
1865:129762. [PMID:
33053413 DOI:
10.1016/j.bbagen.2020.129762]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 08/30/2020] [Accepted: 10/07/2020] [Indexed: 11/29/2022]
Abstract
BACKGROUND
Previous studies have demonstrated the formation of stable complexes between inorganic pyrophosphatase (PPase) and three other Escherichia coli enzymes - cupin-type phosphoglucose isomerase (cPGI), class I fructose-1,6-bisphosphate aldolase (FbaB) and l-glutamate decarboxylase (GadA).
METHODS
Here, we determined by activity measurements how complex formation between these enzymes affects their activities and oligomeric structure.
RESULTS
cPGI activity was modulated by all partner proteins, but none was reciprocally affected by cPGI. PPase activity was down-regulated upon complex formation, whereas all other enzymes were up-regulated. For cPGI, the activation was partially counteracted by a shift in dimer ⇆ hexamer equilibrium to inactive hexamer. Complex stoichiometry appeared to be 1:1 in most cases, but FbaB formed both 1:1 and 1:2 complexes with both GadA and PPase, FbaB activation was only observed in the 1:2 complexes. FbaB and GadA induced functional asymmetry (negative kinetic cooperativity) in hexameric PPase, presumably by favoring partial dissociation to trimers.
CONCLUSIONS
These four enzymes form all six possible binary complexes in vitro, resulting in modulated activity of at least one of the constituent enzymes. In five complexes, the effects on activity were unidirectional, and in one complex (FbaB⋅PPase), the effects were reciprocal. The effects of potential physiological significance include inhibition of PPase by FbaB and GadA and activation of FbaB and cPGI by PPase. Together, they provide a mechanism for feedback regulation of FbaB and GadA biosynthesis.
GENERAL SIGNIFICANCE
These findings indicate the complexity of functionally significant interactions between cellular enzymes, which classical enzymology treats as individual entities, and demonstrate their moonlighting activities as regulators.
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