Can any one help me for a R script to break the protein sequences by enzymatic action.(trypsin). If trypsin breaks protein sequences at K and R, How can i get all the peptide fragments after cutting. K and R for a sequence. Input file is in Fasta format

Input File

sp|Q13515|BFSP2_CON-HUMAN Phakinin OS=Homo sapiens GN=BFSP2 PE=1 SV=1 MSERRVVVDLPTSASSSMPLQRRRASFRGPRSSSSLESPPASRTNAMSGLVRAPGVYVGT

sp|P15924|DESP_CON-HUMAN Desmoplakin OS=Homo sapiens GN=DSP PE=1 SV=3 MSCNGGSHPRINTLGRMIRAESGPDLRYEVTSGGGGTSRMYYSRRGVITDQNSDGYCQTG TMSRHQNQNTIQELLQNCSDCLMRAELIVQPELKYGDGIQLTRSRELDECFAQANDQMEI

Output like: All peptide between of length minimum 10 and max 20 sequnces.

GN=BFSP2

RVVVDLPTSASSSMPLQ RASFRGPRSSSSLESPPASRTNAMSGL KAPGVYVGT