Abstract
E ashbyii incorporates generally-labelled L-[C14] threonine into riboflavin to the extent of 4%. C-1 and C-2 of threonine are incorporated as glycine into C-4a + C-9a of riboflavin. C-3 and C-4 of threonine are not incorporated into riboflavin. The enzyme threonine aldolase, splitting threonine into glycine (C-l + C-2) and acetaldehyde (C-3 + C-4), is present in E. ashbyii.