PP4 Steroid Synthesis

1
PP4Steroid Synthesis StructureChapter 5 pg
113-114ANS 3319Dr. Michael J. Fields
University of Florida
2
Steroid Structure

• Cyclopentanophrenanthrene (Carbon) ring
• Made of carbon, hydrogen, and oxygen
• Soluble in organic solvents
• Molecular weight lt 400

17
12
13
11
16
C
D
1
9
2
10
14
15
8
A
B
3
5
7
6
4
3
Three Classes of Steroids

• Pregnanes (21 Carbons)
• Progesterone
• Androstanes (19 Carbons)
• Testosterone
• Estranes (18 Carbons)
• Estradiol 17ß

O
O
OH
O
OH
HO
4
Steroid Hormone Synthesis

• Acetate ? Mevalonic acid ? Squalene ? Lanosterol
  ? Cholesterol (Cytoplasm)
• Cholesterol ? Pregnenolone (Mitochondria)
• Cholesterol (Sterol) is a precursor to all
  steroids
• Exception is Equilin Equilenin in the pregnant
  mare

5
Steroidogenesis Ovary Testes Adrenal
LH/ACTH
Corticosterone
Delta 5
Delta 4
P4
Cortisol
E1
DHEA
M.J. Fields
E2
T
6
LH Induced Progesterone Synthesis

• LH binds to LHR on cell membrane
• Activates cAMP
• Leads to Kinase A
• Kinase A leads to phosphorylation of the enzyme
  Side Chain Cleavage P450

7
Gonadotropin Induced Steroid Synthesis
Mitochondria
LH
SCCP450
M.J. Fields
8
Site of Steroid Synthesis

• Testes and Ovaries
• Testes can produces all female steroids
• Ovaries can produce all male steroids
• Neither can produce adrenal steroids
• Adrenal gland
• Can produce ALL steroids
• ACTH instead of LH drives the cAMP
• second messenger system

9
Pathway for Steroid Hormone Action
RNA
Nucleus
M.J. Fields