Protein Synthesis Determined from Non-Radioactive Phenylalanine Incorporated by Antarctic Fish

Area of Science:

• Physiological ecology
• Marine biology
• Biochemistry

Background:

• Directly measuring weight gain in slow-growing Antarctic fish is difficult.
• Protein synthesis rate is a crucial indicator of organismal growth.
• Existing methods often involve hazardous radioactive materials and are time-consuming.

Purpose of the Study:

• To develop and validate a non-radioactive methodology for quantifying in vivo protein synthesis rates.
• To assess the robustness of the analytical pathway against potential errors.
• To provide a suitable method for growth characterization in polar fish.

Main Methods:

• Injected ¹³C¹⁵N-labeled phenylalanine into the eelpout (Pachycara brachycephalum).
• Collected muscle tissue at regular intervals (up to 6 hours post-injection).
• Quantified labeled phenylalanine incorporation using liquid chromatography-mass spectrometry (LC-MS).

Main Results:

• Labeled free phenylalanine in the cytosolic fraction increased and plateaued after 4.5 hours.
• Incorporation of labeled phenylalanine into proteins showed a linear increase over time.
• The calculated protein synthesis rate (Ks) was 0.049 ± 0.021% day^-1.

Conclusions:

• The developed non-radioactive method accurately quantifies protein synthesis rates in Antarctic fish.
• This methodology is comparable to traditional radioactive labeling techniques.
• It is a robust and practical approach for in situ growth studies in polar fish.