A possible BioB bipass route

Nearly a decade ago there was something bugging me and I believe I have figured it out —although it's pointless now. Namely, is another way of making biotin possible without using BioB, biotin synthase, an incredibly slow multistep radical SAM enzyme. 

Cysteine racemase: an impossible enzyme?

Cysteine racemase is an enzyme (EC 5.1.1.10) that was characterised in lysates long ago, but have never been found since. Is it a real enzyme? Can the reaction happen well? The problem is that racemising via a carbanion intermediate something with a leaving group is not an easy feat.