Trypsin autolysis

Low-level digests can be dominated by autolysis peaks. The peptide masses (neutral, Mr values) for limit digests of bovine and porcine trypsin are listed below. It is worth screening experimental data for both species, since the labelling of commercial material is not always reliable [Vestling, 1990].

The peaks from porcine trypsin at 841.50 and 2210.10 are often used in MALDI for internal mass calibration. Others peaks which have been observed by MALDI include 514.32, 1044.56, 2282.17, and 2298.17 (2282.17 with oxidised Met) [Parker, 1998].

Porcine trypsin (residues numbered after TRYP_PIG)
Entries in italics are for the variant protein I20 -> V:
From To Mono. Avg. Sequence
52 53 261.14 261.28 SR
54 57 514.32 514.63 IQVR
108 115 841.50 842.01 VATVSLPR
209 216 905.50 906.05 NKPGVYTK
148 157 1005.48 1006.15 APVLSDSSCK
98 107 1044.56 1045.16 LSSPATLNSR
134 147 1468.72 1469.68 SSGSSYPSLLQCLK
217 231 1735.84 1736.97 VCNYVNWIQQTIAAN
116 133 1767.79 1768.99 SCAAAGTECLISGWGNTK
158 178 2157.02 2158.48 SSYPGQITGNMICVGFLEGGK
58 77 2210.10 2211.42 LGEHNIDVLEGNEQFINAAK
78 97 2282.17 2283.63 IITHPNFNGNTLDNDIMLIK
179 208 3012.32 3014.33 DSCQGDSGG…SWGYGCAQK
9 51 4474.09 4477.04 IVGGYTCAA…VVSAAHCYK
9 51 4488.11 4491.07 IVGGYTCAA…VVSAAHCYK

Bovine trypsin (residues numbered after TRY1_BOVIN).
From To Mono. Avg. Sequence
110 111 259.19 259.35 LK
157 159 362.20 362.49 CLK
238 243 632.31 632.67 QTIASN
64 69 658.38 658.76 SGIQVR
112 119 804.41 804.86 SAASLNSR
221 228 905.50 906.05 NKPGVYTK
160 169 1019.50 1020.17 APILSDSSCK
229 237 1110.55 1111.33 VCNYVSWIK
146 156 1152.57 1153.25 SSGTSYPDVLK
207 220 1432.71 1433.65 LQGIVSWGSGCAQK
191 206 1494.61 1495.61 DSCQGDSGGPVVCSGK
70 89 2162.05 2163.33 LGEDNINVVEGNEQFISASK
170 190 2192.99 2194.47 SAYPGQITSNMFCAGYLEGGK
90 109 2272.15 2273.60 SIVHPSYNSNTLNNDIMLIK
120 145 2551.24 2552.91 VASISLPTS…LISGWGNTK
21 63 4550.12 4553.14 IVGGYTCGA…VVSAAHCYK