Functions as a holding molecular chaperone (holdase) which stabilizes unfolding intermediates and rapidly releases them in an active form once stress has abated. Plays an important role in protecting cells from severe heat shock and starvation, as well as in acid resistance of stationary-phase cells. It catalyzes the conversion of methylglyoxal (MG) to D-lactate in a single glutathione (GSH)-independent step (By similarity).