On 2015 Jul 23, Martine Crasnier-Mednansky commented:

The present finding that Salmonella typhimurium transports fructoselysine via a mannose-type PTS (Enzyme IIA^Gfr, IIB^Gfr, IIC^Gfr and IID^Gfr), and uses fructoselysine as a nitrogen source when growing on glucose, deserves some scrutiny. The model established by Doucette CD, 2011 allows coordinated uptake of carbon and nitrogen via inhibition of Enzyme I by α-ketoglutarate, which accumulates in nitrogen limitation. This strategy when applied to the present finding indicates that, when growth occurs on glucose and fructoselysine, both glucose and fructoselysine PTS transports must be regulated to prevent conditions of nitrogen limitation, which will result in both PTS being inhibited. It was reported that the nitrogen PTS, PTS^Ntr (Enzyme I^Ntr, NPr, and Enzyme IIA^Ntr), is activated by α-ketoglutarate (Lee CR, 2013). In this context, it is very tempting to propose that the PTS^Ntr could function to regulate the transcription of the RpoN-dependent gfr operon. Thus, a controlled balance might occur for coordinating PTS-dependent carbon and nitrogen uptakes.

On 2015 Jul 23, Martine Crasnier-Mednansky commented:

The present finding that Salmonella typhimurium transports fructoselysine via a mannose-type PTS (Enzyme IIA^Gfr, IIB^Gfr, IIC^Gfr and IID^Gfr), and uses fructoselysine as a nitrogen source when growing on glucose, deserves some scrutiny. The model established by Doucette CD, 2011 allows coordinated uptake of carbon and nitrogen via inhibition of Enzyme I by α-ketoglutarate, which accumulates in nitrogen limitation. This strategy when applied to the present finding indicates that, when growth occurs on glucose and fructoselysine, both glucose and fructoselysine PTS transports must be regulated to prevent conditions of nitrogen limitation, which will result in both PTS being inhibited. It was reported that the nitrogen PTS, PTS^Ntr (Enzyme I^Ntr, NPr, and Enzyme IIA^Ntr), is activated by α-ketoglutarate (Lee CR, 2013). In this context, it is very tempting to propose that the PTS^Ntr could function to regulate the transcription of the RpoN-dependent gfr operon. Thus, a controlled balance might occur for coordinating PTS-dependent carbon and nitrogen uptakes.