ABSTRACT
The stomac h environmen t i s acidi c a s a resul t o f HC 1 secretio n b y th e
parietal cells . Th e acidi c p H serve s t o denatur e man y proteins , thu s makin g
them susceptibl e t o proteolysis . Th e chie f cell s o f th e stomac h produc e pep -
sinogen, w h i c h i s activate d t o pepsi n b y th e HC 1 (see Tabl e 20.3). T h e opt imu m
p H o f pepti c activit y is aroun d 2, an d pepsin i s inactivated a t neutrality. Anothe r
stomach enzym e i s renni n o r chymosin , w h i c h i s presen t i n infant s bu t no t i n
adults. I t remove s a glycopeptid e fro m milk-K-casein , disruptin g th e casei n
micelle an d promotin g mil k protein coagulatio n an d digestion .
