25660
The available 3 - dimensional structures of these enzymes reveal a typical sortase fold , except for the presence of a unique feature represented by an N - terminal highly flexible loop known as the " lid . " This region interacts with the residues composing the catalytic triad and covers the active site , thus maintaining the enzyme in an autoinhibited state and preventing the accessibility to the substrate .
 Chemical: N
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: N