Bilane is defined as the unsubstituted linear tetrapyrrole with methylene bridges, or the whole class of compounds derived from this single compound by substitution of non-N hydrogens.
Then, for consistency, "hydroxymethylbilane" (HMB) should be defined as the parent bilane with a single substitution of a terminal H by a hydroxymethyl; or the whole class of H-substituted derivatives thereof.
But then preuroporphyrinogen (call it PUPG) is not the same thing as hydroxymethylbilane, in either sense; it is just one specific element of that class. The use of both as synonymous is understandable in biochemistry, because PUPG seems to be the only HMB derivative that occurs in humans and some (most) other living beings. However, now that chemists are playing with artificial porphyrins, that identity does not seem to be justified -- at least for chemists.
Thus I propose to split off the information about PUPG as a separate article, and turn this one into an article on the parent compound and on the whole class. In the head of this article, it will be noted that, in biochemistry, HMB usually means PUPG. Any objections?
--Jorge Stolfi (talk) 04:48, 10 March 2019 (UTC)Reply
