human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: common name, protein name, divergence from human lineage (MYA), accession number, sequence length (aa), sequence identity to human protein
###Question: What is the accession number of the protein with the common name Purple Sea Urchin?
gpt
SELECT accession number FROM table WHERE common name = purple sea urchin