Thank you What do we mean when we say Type 1 PKS enzymes ar

What do we mean when we say Type 1 PKS enzymes are modular? What are the common domains in each module of a Type 1 PKS?

Solution

Type 1 PKS enzymes are modular =

Enzymes in which bicatayst & substrates specificity are separable , multisubstrate enzymes in which binding sites for individual substrates are modular & multienzyme system that catalyze programmable metabolic pathways

Type 1 polyketide synthases consists of very large multifunctional proteins which can be either processive

e.g . unique modular system responsible for synthesis of macrolides like erythromycin ,rapamycin, rifamycin

PKS are multidomain enzymes

Each PKS 1 consists of modules consists of several domains

Modules = from N terminus to C terminus

1] Starting or loading module AT-ACP

2] Elongation or extending module KS-AT-[ DH-ER-KR-]-ACP

3]Termination or releasing module TE

Domains

1] AT- acyltransferase

2]ACP _- acyl carrier protein

3] KS - keto synthase with an SH group on cysteine side chain

4] KR - keto reductase

5] DR- dehydratase

6] ER- enoylreductase

7] MT - methyltransferase

8] SH - sulfahydrolase

9] TH - Thioesterase