Lecture 1: Key Concepts in Amino Acid Metabolism and Agricultural Biotechnology

Incomplete Sentences and Humor

• Example of an incomplete sentence: "Why wasn't the geometry teacher at school?"

• Punchline: "She sprained her angle."

Overview of Biomolecules

• Discussed carbs, lipids, amino acids, and nucleotides.

• "Roundup Ready plants": Genetically modified to withstand glyphosate herbicide.

Glyphosate and Amino Acid Metabolism

• Glyphosate inhibits EPSP enzyme in the shikimate pathway.

• Importance of aromatic amino acids: Tyrosine, tryptophan, phenylalanine.

• Plants cannot survive without synthesizing these amino acids through the shikimate pathway.

• Shikimate pathway must be spelled correctly: s-h-i-k-i-m-a-t-e.

Transgenic Plants and Crop Yield

• Roundup Ready plants are genetically modified to resist glyphosate.

• Allows farmers to spray Roundup without harming crops, increasing yield by 20%.

• Application extends beyond sugar beets to crops like sugar cane, corn, potatoes.

Potential Drawbacks of Herbicide Use

• Environmental implications: Glyphosate can contaminate water systems.

• Risk of developing resistant weed species, leading to agricultural challenges.

Importance of Nitrogen in Biomolecules

• Nitrogen is essential for amino acids and nucleotides, unlike sugars and fats.

• Storage: Amino acids cannot be stored in the body like fats or carbs; excess nitrogen must be excreted as urea.

• Urea is a waste product that has a distinct odor due to nitrogen content.

Amino Acid Basics

• 20 amino acids total; 10 are essential (must be obtained from diet).

• Plants and bacteria can synthesize all 20 amino acids.

• Nitrogen fixation pathways are crucial for incorporating nitrogen into life forms.

  • NH3: ammonia

  • NH4+: ammonium (physiologically relevant)

• 2 Fates of N2

  • Reduction: N2→ NH3 or NH4+

  • Oxidation: N2→ NO2- (nitrates) or NO3- (nitrites)

Pathways and Enzymes

• Focus on amino acid metabolism:

• Glutamate and glutamine are key amino acids.

  • Can make any amino acid from these two

• Biological fixation of nitrogen involves various enzymes, notably nitrogenase in plants and bacteria.

  • nitrogenase enzyme: reduces triple bond in N2 through ATP dependent process that is catalyzed by the nitrogenase complex

  • Glutamine synthetase: plants and bacteria use to convert

• Industrial methods also exist for nitrogen fixation using high temperatures and pressures.

  • N2 from air and H2 from methane under extreme heat and pressure and with a catalyst to make NH3 gas which is cooled to liquid which can be used for things like agricultural, chemicals, pharmaceuticals, and plastics

• Atmospheric fixation: from lightning, breaks N2 triple bond and allows nitrogen to combine with oxygen to form nitrogen oxides. They dissolve in the rain (acid rain)

Amino Acid Synthesis and Transport

• Glutamine synthetase (all organisms) converts glutamate to glutamine; this is crucial for forming new amino acids and nuclei acids.

• Glutamate synthase (plants, bacteria, some insects)

• Glutamate dehydrogenase (all organisms); only active in high concentrations of NH4+

• In nitrogen assimilation:

  • Glutamate has alpha amino group

• The urea cycle is responsible for disposing of excess nitrogen, reinforcing the need to regulate nitrogen levels.

• Glutamate is derived from alpha-ketoglutarate involving ATP and NH4+, also requiring reducing power (NADPH or NADH).

Proteolysis and Amino Acid Turnover

• Proteins are constantly broken down and resynthesized in biological systems.

• Short half-lives of proteins support rapid adaptation to changing cellular environments.

• Specificity of proteases is vital for cellular integrity and control over amino acid availability.