l-carnitine in puppy food Improves Performance Working Dogs in New Study | Nutritional Outlook L-Carnitine for Dogs & Cats:

In fact, research suggests that niacinamide 4% may produce similar results to the prescription antibiotic lotion clindamycin 1%

Takeuchi, K., Maiden, L

A cellular component called glutathione removes potentially harmful oxidants and is itself oxidized to glutathione disulfide in the process

Zhao W, Li Y, Jia L, Pan L, Li H, Du J

Although this will have to be confirmed experimentally, it is interesting to note that poplar GSTF3 and F7 and their close orthologs also have a cysteine at this position, and that fungal Ure2p-like enzymes have an asparagine that was recently assumed to be important for catalysis (Thuillier et al., 2013)