String matching with Cases

Questions
1

I’m trying to get the following to return “pfam03571” from the XML structure.

Cases[ 
  XMLElement[ 
    "myelem", {}, {XMLElement[ 
    "INSDQualifier_value", {}, {"Peptidase family M49; pfam03571"}]}], 
    XMLElement[_, {}, {___~~x:RegularExpression["pfam\\d+"]~~___}]:>x, 
  Infinity]

This doesn’t work. Is this possible without extracting all XMLElement values (I don’t know the element tag name) and using StringCases?

2

This seems to work:

In[22]:= Cases[ 
   XMLElement[ 
     "myelem", {}, {XMLElement[ 
     "INSDQualifier_value", {}, {"Peptidase family M49; pfam03571"}]}], 
   XMLElement[_, {}, {x_String}] /; StringMatchQ[x, RegularExpression[".+pfam\\d+"]] :> x, Infinity] 
Out[22]= {"Peptidase family M49; pfam03571"}
3

Maybe this:

Cases[
 XMLElement["myelem", {}, {XMLElement["INSDQualifier_value", {}, {"Peptidase family M49; pfam03571"}]}]
 ,
 x:_String /; StringMatchQ[x, ___ ~~ "pfam" ~~ DigitCharacter ..] :> StringSplit[x, "; "][[-1]], Infinity]

returning this:

{"pfam03571"}