Exhibit 10.5
Certain information in this document, marked by brackets, has been omitted and
filed separately with the Securities and Exchange Commission. Confidential
treatment has been requested with respect to the omitted portions.

     
(MAXYGEN LOGO) [f40418f4041801.gif]
  Maxygen, Inc.
515 Galveston Drive
Redwood City, CA 94063
650.298.5300 main
650.364.2715 fax
www.maxygen.com

September 24, 2007
Codexis, Inc.
Attn: Doug Sheehy
200 Penobscot Drive
Redwood City, CA 94063

  Re:    License Agreement effective as of March 28, 2002, by and between
Maxygen, Inc. and Codexis, Inc., as amended (the “Agreement”)

Dear Doug:
This letter confirms that, as of the date hereof, SubField 8 of Exhibit G to the
Agreement is hereby deleted in its entirety and replaced with the following:
“SubField 8: Manufacture of fuels, fuel additives and lubricants (and
intermediates of the foregoing) as specified below:

  a.   Manufacture of fuel and/or fuel additives and/or lubricants, where
Biomass (as defined below) is the starting material for the applicable fuel
and/or fuel additive and/or lubricant, including without limitation the
manufacture of compounds (e.g., fermentable sugars) which are intermediates in
the process of producing fuel or fuel additives and/or lubricants, where Biomass
is the starting material for the applicable fuel and/or fuel additive and/or
lubricant and such intermediates are used solely in the production of fuel or
fuel additives and/or lubricants, but specifically excluding the fuels and/or
fuel additives and/or lubricants in Category (b) below.     b.   Conversion of
Biomass-derived oils into fuel and/or fuel additives and/or lubricants,
including without limitation the manufacture of compounds which are
intermediates in the process of converting Biomass-derived oils into fuel and/or
fuel additives and/or lubricants, where such intermediates are used solely in
the production of fuel or fuel additives and/or lubricants.

For purposes of clarification, as used in this SubField 8 (and with regard to
any Supplemental Products that may result due to activation of any Category of
SubField 8), “fuel additives” are substances which are intended to be added to
fuel to modify the characteristics of such fuel, including, for example,
biodegradability, combustibility, viscosity and/or emissions profile, and
“lubricants” are [****].
 

*   Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.

 

--------------------------------------------------------------------------------

 

“Biomass” shall mean [****].
Notwithstanding the above, for purposes of this SubField 8, no right or license
is granted to Codexis to use any Enabling Technology to alter or modify any
gene(s) of any Plant to (a) [****], or (b) [****]; provided, however, Codexis
may produce in Category II Plants chemicals that are Supplemental Products
resulting from the activation of any Category of this SubField 8.”
The parties acknowledge and agree that all of Subfield 8, as amended by this
letter, is subject to that certain letter dated September 11, 2007, and that all
fuels, fuel additives and/or lubricants within amended Subfield 8 shall be
Supplemental Products.
Capitalized terms used but not otherwise defined herein shall have the meanings
set forth in the Agreement.
Please indicate Codexis’ agreement to the foregoing by countersigning below.

            Yours sincerely,
      /s/ Michael S. Rabson       Michael S. Rabson           

          UNDERSTOOD AND AGREED
BY CODEXIS, INC.
    By:   /s/ Douglas Sheehy       Name:   Douglas Sheehy      Title:  
Date: VP & General Counsel
September 24, 2007     

 

*   Certain information on this page has been omitted and filed separately with
the Securities and Exchange Commission. Confidential treatment has been
requested with respect to the omitted portions.