You can identify your matched peptides using your mass values and 1st hit best matched protein sequence from Mascot site. Further, your can search protein blast for identify perfect template for your matched peptides. Also, there are plenty of servers providing template information for unknown proteins.
NCBI basic program Blastp program has "Align two sequences" page. You can paste template protein in the top box and the peptide sequence in the second box and just hit "Blast" button.
You can screen major database, such as UniProt for all known protein sequences containing your peptide. You can use BLAST program. It's available for instance here:
http://www.ebi.ac.uk/services/proteins
If you know template protein sequence you may use e.g. Clustal W: