NADP-linked dehydrogenases in secreted milk

Area of Science:

• Biochemistry
• Mammalian Physiology
• Enzymology

Background:

• Mammary gland enzymes are crucial for milk production and composition.
• Understanding milk enzyme activity can provide insights into mammary gland function.

Purpose of the Study:

• To determine and compare the activities of key metabolic enzymes in milk from sows, rats, and rabbits.
• To assess whether milk enzyme activity patterns accurately reflect those in the mammary gland.

Main Methods:

• Enzyme activity assays were performed on secreted milk samples from three species.
• Enzyme activities measured included glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, isocitrate dehydrogenase, malic enzyme, lactate dehydrogenase, and malate dehydrogenase.
• Results were compared to previously published data for mammary homogenates.

Main Results:

• Relative enzyme activities in milk were generally consistent with those found in mammary homogenates across all species studied.
• Significant variations in absolute enzyme activities were observed within each species.
• A notable exception was glucose 6-phosphate dehydrogenase, which showed reduced activity in milk upon prolonged storage within the mammary gland.

Conclusions:

• The enzyme activity profile in secreted milk serves as a reliable indicator of the enzyme pattern within the mammary gland.
• Milk enzyme analysis offers a non-invasive method to infer mammary gland metabolic status.
• Storage conditions can impact specific enzyme activities, such as glucose 6-phosphate dehydrogenase, in milk.