The word "PEPSC" refers to the enzyme pepsinogen, which is secreted by the stomach and then converted to pepsin, an enzyme that aids in the digestion of proteins. Its spelling can be explained through the use of the International Phonetic Alphabet (IPA) as pɛpsk. The letter "c" is used to represent the hard "k" sound at the end of the word. The combination of the letters "ps" suggests the presence of the sound /ps/ in the pronunciation of the word.