Term of Award

Summer 2022

Degree Name

Master of Science in Applied Physical Science (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


Department of Chemistry and Biochemistry

Committee Chair

Mitch Weiland

Committee Member 1

Nathaniel Shank

Committee Member 2

Beverly Penland


Due to the accumulation of polymers in the environment, biodegradable alternatives should be used in place of commonly used polymers like poly(carboxylates). Poly(carboxylates) are water-soluble polymers (WSPs) that make up a variety of consumer products, such as detergents, descaling agents, and superabsorbent materials commonly found in diapers and feminine hygiene products. While the visible accumulation of these products may not be obvious, it is necessary to reduce the amount entering the environment. Poly(aspartic acid) (PAA) is an alternative WSP that is biodegradable through the action of three different enzymes, PahZ1KT-1, PahZ2KT-1, and PahZ1KP-2. Originally isolated from river water bacteria strains Sphingomonas sp. KT-1 and Pedobactor sp. KP-2, these enzymes were reported to break down poly(aspartic acid) to the original monomer, aspartic acid. PahZ1KT-1, a serine protease, cleaves β-amide linkages to form oligo(aspartic acid) (OAA), which is then acted upon by PahZ2KT-1. PahZ2KT-1 acts upon both α- and β- amide linkages,forming monomeric aspartic acid as a product, and requires the presence of zinc ions in the active site for catalytic activity. PahZ1KP-2, a PahZ1KT-1 homolog, is a putative serine protease that cleaves high-molecular weight PAA at the β-amide linkage. This thesis focuses on the characterization of these needed poly(aspartic acid) degrading enzymes through elucidation of their crystal structures and important residues for catalytic activity and substrate binding. Structural and functional knowledge of each enzyme will allow for protein engineering to enhance poly(aspartic acid) degradation and future degradation of other WSPs.

Research Data and Supplementary Material


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Biochemistry Commons