TABLE 1.

Parameters central to the enzyme model

Symbol	Description	Unit	Value
α	Enzyme (E) decay rate	1/s	1/(7 × 24 × 3,600)a
β	Reaction constant	m3/(s mol)	4.1 × 103b
DE	Diffusivity of enzymes	m2/s	5 × 10−11
DM	Diffusivity of monomer	m2/s
DP	Diffusivity of polymer	m2/s	5 × 10−11
a	Radius of spherical cell	m	0.3 × 10−6c
Q	Production rate of enzyme	mol/s	1.8 × 10−24
P∞	Background polymer concn	mol/m3	P∞d

^aBased on measurements of extracellular enzymes in seawater (34, 41).

^bAlso called the specificity constant and defined as k_cat/K_m for the specific enzyme-substrate complex. The value is based on an average of bacterial psychrophilic and mesophilic α-amylases (40).

^cTypical cell size of planktonic marine bacteria (64).

^dThe oceans typically contain 30 to 80 μmol C kg⁻¹ in the dissolved organic carbon fraction (65), and from the perspective of a single planktonic cell, the potential substrate field would indeed appear infinite.