To answer this question: How do I do something similar and download a list of all genes involved in metabolism?
My go-to is usually the Comparative Toxicogenomics Database.
You can download the data files here in csv and tsv formats.
If for example you download the csv.gz file. You can extract it (gunzip) and then grep it for your search term using something like this:
grep R-HSA-1430728 your/file/path/here/CTD_genes_pathways.csv | cut -d ',' -f1 | sort | uniq
The command will search for R-HSA-1430728, cut the gene out (cutting the first word detecting commas as the separator), sort the genes alphabetically, and then give only the unique gene names (removes deplicates).
Note: I obtained 2171 unique genes using the command above (not 2325 genes):
grep R-HSA-1430728 your/file/path/here/CTD_genes_pathways.csv | cut -d ',' -f1 | sort | uniq | wc -l
2171
Hope this helps!