precursor

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precursor

 [pre-ker´ser]
something that precedes. In biological processes, a substance from which another, usually more active or mature substance, is formed. In clinical medicine, a sign or symptom that heralds another.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pre·cur·sor

(prē-kŭr'sŏr),
That which precedes another or from which another is derived, applied especially to a physiologically inactive substance that is converted to an active enzyme, vitamin, hormone, etc., or to a chemical substance that is built into a larger structure in the course of synthesizing the latter.
[L. praecursor, fr. prae-, pre- + curro, to run]
Farlex Partner Medical Dictionary © Farlex 2012

precursor

(prĭ-kûr′sər, prē′kûr′sər)
n.
A biochemical substance, such as an intermediate compound in a chain of enzymatic reactions, from which a more stable or definitive product is formed: a precursor of insulin.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

pre·cur·sor

(prē'kŭrs-ŏr)
That which precedes another or from which another is derived, applied especially to a physiologically inactive substance that is converted to an active enzyme, vitamin, or hormone, or to a chemical substance that is built into a larger structure in the course of synthesizing the latter.
[L. praecursor, fr. prae-, pre- + curro, to run]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

precursor

a form that precedes another. For example:
  1. (a) a substance that precedes and is involved in the synthesis of a compound, such as any of the intermediates in the synthesis of an AMINO ACID.
  2. (b) a cell from which other cells develop.
  3. (c) a molecule that is subjected to modification to provide an active molecule, such as the enzymic cleavage of TRYPSINOGEN to yield TRYPSIN (see ZYMOGEN).
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

pre·cur·sor

(prē'kŭrs-ŏr)
That which precedes another or from which another is derived.
[L. praecursor, fr. prae-, pre- + curro, to run]
Medical Dictionary for the Dental Professions © Farlex 2012