Zinc function

• Protein structure
  • Forms bonds between cysteine and histidine
  • Forms zinc finger transcription factors
    • Zinc finger: a type of DNA-binding domain, binded by transcription factors
      • Characteristics: zinc ion coordinated by two histidine and two cysteine residues
      • DNA binding: Several zinc finger domains are often connected as a chain and bind to an α-helix in the major groove of DNA.
• Aids in maintenance and stability of the nuclear membrane
• Essential part of many enzymes (> 100), including DNA polymerase, carbonic anhydrase, ACE, alkaline phosphatase, metallothionein, superoxide dismutase, and collagenases

Zinc deficiency

• Causes
  • Inadequate dietary intake
  • Acrodermatitis enteropathica: congenital deficiency of the zinc/iron-regulated transporter-like protein (ZIP)
  • Malabsorption (e.g., due to Crohn disease), liver, and renal disease
  • Total parenteral nutrition (TPN)
  • Chronic liver disease (esp. liver cirrhosis)
  • Bowel resection
• Clinical features
  • Impaired wound healing
    • Inability to replace type III collagen with type I collagen
  • Dysgeusia
    • On the upper surface of the tongue, there are taste receptor cells known as "taste buds". These cells regenerate frequently but the activity reduces when zinc is deficient, which causes dysgeusia.
  • Anosmia
  • Immune dysfunction
  • Male hypogonadism
  • Dermatitis
    • Perioral (a) and perianal (b) erythema and pustules can be seen.
  • Alopecia
  • In patients with liver cirrhosis: associated with accelerated progression of cirrhosis and aggravated clinical symptoms (e.g., hepatic encephalopathy)
  • Diarrhea
  • Impaired growth and development
• Diagnosis: measurement of plasma zinc levels
• Treatment: oral zinc supplementation