IN the scheme proposed by Astrup1 to represent the stages in the activation of human plasminogen to plasmin by streptokinase, the substance designated ‘proactivator’ has hitherto been a hypothetical one, postulated to account for certain observations made by Astrup and his co-workers, but never isolated by them. American workers, notably Sherry et al. 2, have doubted the existence of proactivator, pointing out that all procedures available for the purification of human plasminogen result in parallel purification of the proactivator activity. Ablondi and Hagan3 think that proactivator and plasminogen are probably identical.
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Archives of Oto-Rhino-Laryngology (1979)