TreS-Mak-GlgE branched alpha-glucan biosynthesis

A reusable bacterial pathway that channels trehalose into branched alpha-glucan. Trehalose synthase operating in the catabolic direction forms maltose, maltokinase converts maltose to alpha-maltose 1-phosphate, GlgE uses that activated donor to extend alpha-1,4-glucan chains by maltosyl units, and GlgB introduces alpha-1,6 branches. TreS and Mak may be separate proteins or domains of one fusion protein; that architectural variation does not change the four reaction roles.

The Pseudomonas putida KT2440 implementation uses a bifunctional TreS-Mak fusion (TreSB), represented as the same UniProt exemplar in two reaction leaves. This is an implementation detail, not a reason to merge the reactions. The module starts with trehalose and ends with branched alpha-glucan; trehalose biosynthesis, glucan priming, degradation, and downstream storage-envelope roles are outside its boundary. The broad GO terms used for Mak and GlgE are supplemented by exact EC and Rhea chemistry.