Improved hair straightening topical compositions comprising transglutaminase, sodium metabisulfite, and a system for stabilizing the pH of the composition, and for inhibiting the generation of sulfur dioxide. Optionally, one or more additional hair straightening agents, that are capable of affecting secondary, tertiary and quaternary protein structures of human hair may be included. Optionally, polylysine may be included which, in combination with TGase, acts to form a surface barrier film and moisture shield around human hair. The invention includes methods of using such topical compositions.