The liver synthesizes and releases a protein called angiotensinogen.
This is then broken up by renin, an enzyme produced in the kidney, to form angiotensin 1.
Angiotensin -1 is formed from angiotensinogen by the action of renin, which is released from the kidney juxtaglomerular cells.
The factor that converts angiotensinogen into angiotensin-1:
Renin, produced by the kidney, in response to glomerular hypoperfusion, catalyzes the cleavage of angiotensinogen to angiotensin-1, an inactive decapeptide.
Angiotensin-1 is in turn cleaved by the angiotensin-converting enzyme (ACE) to produce angiotensin 2.
Hence, angiotensinogen is converted to angiotensin-1 by renin.