BCHS 3304 Lecture Notes - Lecture 18: Serine Protease, Substrate Analog, Chymotrypsin
17 Nov 2016
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Lecture 18: always have a ser-his- asp triade at the active site. Specificity pockets of the three: have very reactive ser residue at their active site. Dipf reacts with the active ser residue only. Thus, it helps you find the ser protease. Generally ser is unreactive: his residue is a second catalytic residue. Chymotrypsin has preference for cleaving next to phe. Substrate analog binds to chymotrypsin active site. Catalytic his reacts with the acid chloride. Mimics lysine: bovine trypsin and its inhibitor leupeptin. These 3 residues are hydrogen bonded together. Located next to the pocket of specificity determine which substrates the enzyme recognizes: trypsin: pocket of gly, asp, gly. Fairly bulky residues can fit in the pocket: chymotrypsin: pocket of gly, ser, gly. Bulky residues can fit in the: elastase: pocket of val, thr pocket. Only relatively small residues can fit in the pocket: convergent evolution. Chymotrypsin, trypsin, elastase are very similar in sequence and function.
