substrate

1. The substance acted upon and changed by an enzyme; the reactant considered to be attacked in a chemical reaction. 2. The base on which an organism lives or grows; e.g., the s. on which microorganisms and cells grow in cell culture. [L. sub-sterno, pp. -stratus, to spread under]

- insulin receptor s.-1 a cytoplasmic protein that is a direct s. of the activated insulin receptor kinase. Insulin exposure results in its rapid phosphorylation at multiple tyrosine residues. Its phosphorylated sites associate with high affinity to certain cellular proteins. IRS-1 thus acts as an adaptor molecule that links the receptor kinase to various cellular activities regulated by insulin. IRS-1 is also phosphorylated after stimulation by insulinlike growth factor-1 and several interleukins.

- suicide s. a competitive inhibitor that is converted to an irreversible inhibitor at the active site of the enzyme. SYN: mechanism-based inhibitor, suicide inhibitor.

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sub·strate 'səb-.strāt n

1) SUBSTRATUM (1)

2) the base on which an organism lives

3) a substance acted upon (as by an enzyme)

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n.

the specific substance or substances on which a given enzyme acts. For example, starch is the substrate for salivary amylase; RNA is the substrate for ribonuclease.

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sub·strate (subґstrāt) 1. a substance upon which an enzyme acts. Symbol S. 2. a neutral substance containing a nutrient solution. 3. a surface upon which a different material is deposited or adhered, usually in a coating or layer.