The MdProfile element (in the Header section) contains a unique profile code (e.g.: clarin.eu:cr1:p_1290431694484). Alternatively you can also find the profile identifier as part of the schema location, for example (CMDI 1.1):
<CMD ... xsi:schemaLocation="http://www.clarin.eu/cmd/ http://catalog.clarin.eu/ds/ComponentRegistry/rest/registry/1.1/profiles/clarin.eu:cr1:p_1290431694484/xsd">
or (CMDI 1.2):
<cmd:CMD ... xsi:schemaLocation="http://www.clarin.eu/cmd/1 https://infra.clarin.eu/CMDI/1.x/xsd/cmd-envelop.xsd http://www.clarin.eu/cmd/1/profiles/clarin.eu:cr1:p_1381926654508 https://catalog.clarin.eu/ds/ComponentRegistry/rest/registry/1.x/profiles/clarin.eu:cr1:p_1290431694484/xsd">
You can find the profile in the component registry with the following URL:
http://catalog.clarin.eu/ds/ComponentRegistry?item=*code*
e.g. http://catalog.clarin.eu/ds/ComponentRegistry?item=clarin.eu:cr1:p_1345561703620