linguistic:paraphrasing, stylistic:style_transfer, quality:correction, quality:corruption
Selenophosphate synthetase

Among prokaryotes, most bacteria have a version with cystine instad of selenocystine, suggesting that this may be the ancestral state (which would avoid the chicken-and-egg problem). Some have two versions, one with Sec and the other with Cys. Archaea mostly have the Sec version.