On 2016 Mar 07, Martine Crasnier-Mednansky commented:

Escherichia coli cells, when 'pre-induced' in the presence of the artificial inducer TMG, synthesize β-galactosidase in the presence of glucose. COHN M, 1959 stated: "The effect of pre-induction is to restore in the presence of 10^-3 M glucose about 50 per cent of the maximal differential rate obtainable on succinate". The observation the maximal rate was not reached in the presence of glucose led the authors to argue, indeed incorrectly, that glucose was a preferential metabolic source for yielding high internal levels of repressor. Such observation however will have an explanation later on with the discovery of the 'cAMP effect' on β-galactosidase synthesis, in agreement with the finding by COHN M, 1959 that carbon sources presently known to elicit higher cAMP levels (particularly succinate, lactate and glycerol, see Epstein W, 1975) were found to be non-inhibitory (i.e. allowing maximal differential rate). Anke Becker’s final statement, that inhibition of lactose permease by unphosphorylated Enzyme IIA^Glc (leading to inducer exclusion) is primarily responsible for CCR of the lac operon, is therefore inappropriate as cAMP via its receptor protein (simultaneously designated as CRP Emmer M, 1970 and CAP Zubay G, 1970) also plays a role in CCR of the lac operon. Furthermore, Jacques Monod (1942) reported diauxie was attenuated - but not eliminated - when the cells were pre-induced (adapted to the less preferred 'B' sugar). Diauxie was however eliminated by addition of exogenous cAMP Ullmann A, 1968. Therefore, inducer exclusion and the level of cAMP both contribute to CCR of the lac operon.

Lastly, unphosphorylated EIIA^Glc does not inhibit adenylate cyclase. The current model of regulation postulates dephosphorylation of Enzyme IIA^Glc during glucose transport interferes with the activation of adenylate cyclase by phosphorylated Enzyme IIA^Glc.

On 2016 Mar 07, Martine Crasnier-Mednansky commented:

Escherichia coli cells, when 'pre-induced' in the presence of the artificial inducer TMG, synthesize β-galactosidase in the presence of glucose. COHN M, 1959 stated: "The effect of pre-induction is to restore in the presence of 10^-3 M glucose about 50 per cent of the maximal differential rate obtainable on succinate". The observation the maximal rate was not reached in the presence of glucose led the authors to argue, indeed incorrectly, that glucose was a preferential metabolic source for yielding high internal levels of repressor. Such observation however will have an explanation later on with the discovery of the 'cAMP effect' on β-galactosidase synthesis, in agreement with the finding by COHN M, 1959 that carbon sources presently known to elicit higher cAMP levels (particularly succinate, lactate and glycerol, see Epstein W, 1975) were found to be non-inhibitory (i.e. allowing maximal differential rate). Anke Becker’s final statement, that inhibition of lactose permease by unphosphorylated Enzyme IIA^Glc (leading to inducer exclusion) is primarily responsible for CCR of the lac operon, is therefore inappropriate as cAMP via its receptor protein (simultaneously designated as CRP Emmer M, 1970 and CAP Zubay G, 1970) also plays a role in CCR of the lac operon. Furthermore, Jacques Monod (1942) reported diauxie was attenuated - but not eliminated - when the cells were pre-induced (adapted to the less preferred 'B' sugar). Diauxie was however eliminated by addition of exogenous cAMP Ullmann A, 1968. Therefore, inducer exclusion and the level of cAMP both contribute to CCR of the lac operon.

Lastly, unphosphorylated EIIA^Glc does not inhibit adenylate cyclase. The current model of regulation postulates dephosphorylation of Enzyme IIA^Glc during glucose transport interferes with the activation of adenylate cyclase by phosphorylated Enzyme IIA^Glc.