 These two loops can vary between each PLA1.For example, a PLA1 enzyme with a long lid domain (22-23 amino acids) and a long B9 domain (18-19 amino acids) constitute an extracellular PLA1 exhibiting triacylglycerol hydrolase activity.In contrast, a PLA1 enzyme that is considered more selective will have a short lid and B9 domain that span 7-12 and 12-13 amino acids, respectively.