Glutamine
Glutamine is the most abundant naturally occurring, nonessential amino acid in the human body, and one of the few amino acids that can directly cross the blood–brain barrier. Humans obtain glutamine through catabolism of proteins in foods they eat. In states where tissue is being built or repaired, like growth of babies, or healing from wounds or severe illness, glutamine becomes conditionally essential.
Titin
Titin is the largest known protein; its human variant consists of 34,350 amino acids, with the molecular weight of the mature "canonical" isoform of the protein being approximately 3,816,188.13 Da. Its mouse homologue is even larger, comprising 35,213 amino acids with a MW of 3,906,487.6 Da. It has a theoretical isoelectric point of 6.01. The protein's empirical chemical formula is CHNOS. It has a theoretical instability index (II) of 42.41, classifying the protein as unstable. The protein's in vivo half-life, the time it takes for half of the amount of protein in a cell to break down after its synthesis in the cell, is predicted to be approximately 30 hours (in mammalian reticulocytes).