Aminomutase that catalyzes the transfer of the amine group on carbon 2 of glutamate 1-semialdehyde to the adjacent carbon 1 to form 5-aminolevulinate. (S)-4-amino-5-oxopentanoate = 5-aminolevulinate Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; 5-aminolevulinate from L-glutamyl-tRNA(Glu): step 2/2. Homodimer. Induced by low extracellular levels of magnesium via the PhoQ/PhoP two-component regulatory system. Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family. HemL subfamily.