This seems rather pedantic to me. You first declared there’s no such thing as “the beta-lactamase fold” because, you said, it’s a structural classification. But they just ARE named for the functions of proteins in actual databases.
Heck, in the CATH database that IS the full and only name for the fold(topology level in the CATH hierarchy):
https://www.cathdb.info/browse/sunburst?from_cath_id=3.40.710
Experimentally-determined protein three-dimensional structures are obtained from the Protein Data Bank and split into their consecutive polypeptide chains, where applicable. Protein domains are identified within these chains using a mixture of automatic methods and manual curation. The domains are then classified within the CATH structural hierarchy: at the Class (C) level, domains are assigned according to their secondary structure content, i.e. all alpha, all beta, a mixture of alpha and beta, or little secondary structure; at the Architecture (A) level, information on the secondary structure arrangement in three-dimensional space is used for assignment; at the Topology/fold (T) level, information on how the secondary structure elements are connected and arranged is used; assignments are made to the Homologous superfamily (H) level if there is good evidence that the domains are related by evolution, i.e. they are homologous. To browse the classification hierarchy, see CATH hierarchy.
What’s the topology/fold level called for serine beta-lactamases in the CATH database? That’s right, beta-lactamase. And nothing else.
Annoyingly there isn’t even really a fully consistent terminology on this.
Yes and for early characterized proteins those proteins in turn were usually named for the functions they were first known to perform (and the names also changed along the way, they used to be called penicillinases IIRC). Hence, the fold is named for the functions known at the time.
It’s just not clear to me why the use of the term is a mistake when, in point of fact, the name appears in widely used databases for a range of similar structures.
As for whether this is in the end a good name for the structure to hang on to, since many other functions are known for it, is hardly a fact we can blame the DI for. As much as I think they spew a lot of nonsense at the DI I’m not persuaded their use of this name for the fold is intentionally misleading, even if it ultimately might mislead someone who isn’t aware that it’s just a name and not a functional classification.