8513
We propose an extended functionality of Asp - 168 , which acts like a gatekeeper by altering the width of the heme cavity access channel .
 Chemical: Asp; Chemical: heme
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: Asp, heme 
Answer:
 Chemical: Asp; Chemical: heme